Dual catalyst system for ebullated bed upgrading to produce improved quality vacuum residue product

ABSTRACT

An ebullated bed hydroprocessing system is upgraded using a dual catalyst system that includes a heterogeneous catalyst and dispersed metal sulfide particles to improve the quality of vacuum residue. The improved quality of vacuum residue can be provided by one or more of reduced viscosity, reduced density (increased API gravity), reduced asphaltene content, reduced carbon residue content, reduced sulfur content, and reduced sediment. Vacuum residue of improved quality can be produced while operating the upgraded ebullated bed reactor at the same or higher severity, temperature, throughput and/or conversion. Similarly, vacuum residue of same or higher quality can be produced while operating the upgraded ebullated bed reactor at higher severity, temperature, throughput and/or conversion.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims the benefit of U.S. Provisional PatentApplication No. 62/347,304, filed Jun. 8, 2016, the disclosure of whichis incorporated herein in its entirety.

BACKGROUND OF THE INVENTION 1. The Field of the Invention

The invention relates to heavy oil hydroprocessing methods and systems,such as ebullated bed hydroprocessing methods and systems, which utilizea dual catalyst system to produce upgraded hydrocarbon products,including vacuum residue product of improved quality.

2. The Relevant Technology

There is an ever-increasing demand to more efficiently utilize lowquality heavy oil feedstocks and extract fuel values therefrom. Lowquality feedstocks are characterized as including relatively highquantities of hydrocarbons that nominally boil at or above 524° C. (975°F.). They also contain relatively high concentrations of sulfur,nitrogen and/or metals. High boiling fractions derived from these lowquality feedstocks typically have a high molecular weight (oftenindicated by higher density and viscosity) and/or low hydrogen/carbonratio, which is related to the presence of high concentrations ofundesirable components, including asphaltenes and carbon residue.Asphaltenes and carbon residue are difficult to process and commonlycause fouling of conventional catalysts and hydroprocessing equipmentbecause they contribute to the formation of coke and sediment.Furthermore, carbon residue places limitations on downstream processingof high boiling fractions, such as when they are used as feeds forcoking processes.

Lower quality heavy oil feedstocks which contain higher concentrationsof asphaltenes, carbon residue, sulfur, nitrogen, and metals includeheavy crude, oil sands bitumen, and residuum left over from conventionalrefinery process. Residuum (or “resid”) can refer to atmospheric towerbottoms and vacuum tower bottoms. Atmospheric tower bottoms can have aboiling point of at least 343° C. (650° F.) although it is understoodthat the cut point can vary among refineries and be as high as 380° C.(716° F.). Vacuum tower bottoms (also known as “resid pitch” or “vacuumresidue”) can have a boiling point of at least 524° C. (975° F.),although it is understood that the cut point can vary among refineriesand be as high as 538° C. (1000° F.) or even 565° C. (1050° F.).

By way of comparison, Alberta light crude contains about 9% by volumevacuum residue, while Lloydminster heavy oil contains about 41% byvolume vacuum residue, Cold Lake bitumen contains about 50% by volumevacuum residue, and Athabasca bitumen contains about 51% by volumevacuum residue. As a further comparison, a relatively light oil such asDansk Blend from the North Sea region only contains about 15% vacuumresidue, while a lower-quality European oil such as Ural contains morethan 30% vacuum residue, and an oil such as Arab Medium is even higher,with about 40% vacuum residue. These examples highlight the importanceof being able to convert vacuum residues when lower-quality crude oilsare used.

Converting heavy oil into useful end products involves extensiveprocessing, such as reducing the boiling point of the heavy oil,increasing the hydrogen-to-carbon ratio, and removing impurities such asmetals, sulfur, nitrogen and coke precursors. Examples of hydrocrackingprocesses using conventional heterogeneous catalysts to upgradeatmospheric tower bottoms include fixed-bed hydroprocessing,ebullated-bed hydroprocessing, and moving-bed hydroprocessing.Noncatalytic upgrading processes for upgrading vacuum tower bottomsinclude thermal cracking, such as delayed coking, flexicoking,visbreaking, and solvent extraction.

SUMMARY OF THE INVENTION

Disclosed herein are methods for upgrading an ebullated bedhydroprocessing system to convert hydrocarbon products from heavy oiland produce vacuum residue products of improved quality. Also disclosedare methods and upgraded ebullated bed hydroprocessing systems toconverted hydrocarbon products and produce vacuum residue products ofimproved quality. The disclosed methods and systems involve the use of adual catalyst system comprised of a solid supported (i.e.,heterogeneous) catalyst and well-dispersed (e.g., homogeneous) catalystparticles. The dual catalyst system can be employed to upgrade anebullated bed hydroprocessing system that otherwise utilizes a singlecatalyst composed of a solid supported ebullated bed catalyst.

In some embodiments, a method of upgrading an ebullated bedhydroprocessing system to produce converted products from heavy oil,including vacuum residue products of improved quality, comprises: (1)operating an ebullated bed reactor using a heterogeneous catalyst tohydroprocess heavy oil and produce converted products, including avacuum residue product of initial quality; (2) thereafter upgrading theebullated bed reactor to operate using a dual catalyst system comprisedof dispersed metal sulfide catalyst particles and heterogeneouscatalyst; and (3) operating the upgraded ebullated bed reactor toproduce converted products, including a vacuum residue product ofimproved quality compared to when initially operating the ebullated bedreactor.

The quality of a vacuum residue product of a given boiling point orrange is typically understood to be a function of the viscosity,density, asphaltene content, carbon residue content, sulfur content, andsediment content. It may also involve nitrogen content and metalscontent. The methods and systems disclosed herein produce vacuum residueproducts having improved quality as defined by one or more of: (a)reduced viscosity, (b) reduced density (increased API gravity), (c)reduced asphaltene content, (d) reduced carbon residue content, (e)reduced sulfur content, (f) reduced nitrogen content, and (g) reducedsediment content. In some or most cases, more than one of the qualityfactors is improved, and in many cases, most or all of the qualityfactors can be improved, including at least reduced viscosity, reducedasphaltene content, reduced carbon residue content, reduced sulfurcontent, and reduced sediment content.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in viscosity (e.g., as measured byBrookfield Viscosity at 300° F.) of at least 10%, 15%, 20%, 25%, 30%,40%, 50%, 60%, or 70% compared to when initially operating the ebullatedbed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in asphaltene content of at least 5%,7.5%, 10%, 12.5%, 15%, 20%, 25%, or 30% compared to when initiallyoperating the ebullated bed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in micro carbon residue content (e.g.,as measured by MCR content) of at least 2%, 4%, 6%, 8%, 10%, 12.5%, 15%,or 20% compared to when initially operating the ebullated bed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in sulfur content of at least 5%, 7.5%,10%, 15%, 20%, 25%, 30%, or 35% compared to when initially operating theebullated bed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in density, which can be expressed as anincrease in ° API Gravity of at least 0.4, 0.6, 0.8, 1.0, 1.3, 1.6, 2.0,2.5 or 3.0, compared to when initially operating the ebullated bedreactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in sediment content of at least 2%, 4%,6%, 8%, 10%, 12.5%, 15%, or 20% compared to when initially operating theebullated bed reactor.

In general, vacuum residue products can be used for fuel oil, solventdeasphalting, coking, power plant fuel, and/or partial oxidation (e.g.,gasification to generate hydrogen). Because of restrictions on theamount of contaminants that are permitted in fuel oil, improving thequality of vacuum residue products using the dual catalyst systemhydroprocessing systems disclosed herein can reduce the amount of moreexpensive cutter stocks otherwise required to bring the vacuum residuewithin specification. It can also reduce the burden on the overallprocess where the cutter stock can be utilized elsewhere for moreefficient operation of the overall hydroprocessing system.

In some embodiments, the dispersed metal sulfide catalyst particles areless than 1 μm in size, or less than about 500 nm in size, or less thanabout 250 nm in size, or less than about 100 nm in size, or less thanabout 50 nm in size, or less than about 25 nm in size, or less thanabout 10 nm in size, or less than about 5 nm in size.

In some embodiments, the dispersed metal sulfide catalyst particles areformed in situ within the heavy oil from a catalyst precursor. By way ofexample and not limitation, the dispersed metal sulfide catalystparticles can be formed by blending a catalyst precursor into anentirety of the heavy oil prior to thermal decomposition of the catalystprecursor and formation of active metal sulfide catalyst particles. Byway of further example, methods may include mixing a catalyst precursorwith a diluent hydrocarbon to form a diluted precursor mixture, blendingthe diluted precursor mixture with the heavy oil to form conditionedheavy oil, and heating the conditioned heavy oil to decompose thecatalyst precursor and form the dispersed metal sulfide catalystparticles in situ within the heavy oil.

These and other advantages and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 depicts a hypothetical molecular structure of asphaltene;

FIGS. 2A and 2B schematically illustrate exemplary ebullated bedreactors;

FIG. 2C schematically illustrates an exemplary ebullated bedhydroprocessing system comprising multiple ebullated bed reactors;

FIG. 2D schematically illustrates an exemplary ebullated bedhydroprocessing system comprising multiple ebullated bed reactors and aninterstage separator between two of the reactors;

FIG. 3A is a flow diagram illustrating an exemplary method for upgradingan ebullated bed reactor to produce a vacuum residue product of improvedquality while operating the reactor at similar or higher severity;

FIG. 3B is a flow diagram illustrating an exemplary method for upgradingan ebullated bed reactor to produce a vacuum residue product of improvedquality while operating the reactor at similar or higher throughput;

FIG. 3C is a flow diagram illustrating an exemplary method for upgradingan ebullated bed reactor to produce a vacuum residue product of improvedquality while operating the reactor at similar or higher conversion;

FIG. 3D is a flow diagram illustrating an exemplary method for upgradingan ebullated bed reactor to produce a vacuum residue product of same orimproved quality while operating the reactor at higher severity,throughput and/or conversion;

FIG. 4 schematically illustrates an exemplary ebullated bedhydroprocessing system using a dual catalyst system including aheterogeneous catalyst and dispersed metal sulfide catalyst particles;

FIG. 5 schematically illustrates a pilot scale ebullated bedhydroprocessing system configured to employ either a heterogeneouscatalyst by itself or a dual catalyst system including a heterogeneouscatalyst and dispersed metal sulfide catalyst particles;

FIG. 6 is a line graph graphically representing differences in theBrookfield Viscosity (measured at 300° F. (149° C.)) of vacuum residueproducts having a boiling point of 1000° F.+(538° C.+) produced whenhydroprocessing a heavy oil feedstock (Ural vacuum residuum) usingdifferent dispersed metal sulfide catalyst particle concentrations andat different resid conversions according to Examples 1-6;

FIG. 7 is a line graph graphically representing differences in thesulfur content of vacuum residue products having a boiling point of1000° F.+(538° C.+) produced when hydroprocessing Ural heavy oilfeedstock using different dispersed metal sulfide catalyst particleconcentrations and at different resid conversions according to Examples1-6;

FIG. 8 is a line graph graphically representing differences in the C₇asphaltene content of vacuum residue products having a boiling point of1000° F.+(538° C.+) produced when hydroprocessing Ural heavy oilfeedstock using different dispersed metal sulfide catalyst particleconcentrations and at different resid conversions according to Examples1-6;

FIG. 9 is a line graph graphically representing differences in thecarbon residue content (by MCR) of vacuum residue products having aboiling point of 1000° F.+(538° C.+) produced when hydroprocessing Uralheavy oil feedstock using different dispersed metal sulfide catalystparticle concentrations and at different resid conversions according toExamples 1-6;

FIG. 10 is a line graph graphically representing differences in the °API Gravity of vacuum residue products having a boiling point of 1000°F.+(538° C.+) produced when hydroprocessing a heavy oil feedstock (ArabMedium vacuum residuum) using different dispersed metal sulfide catalystparticle concentrations and at different resid conversions according toExamples 7-13;

FIG. 11 is a line graph graphically representing differences in thesulfur content of vacuum residue products having a boiling point of1000° F.+(538° C.+) produced when hydroprocessing Arab Medium heavy oilfeedstock using different dispersed metal sulfide catalyst particleconcentrations and at different resid conversions according to Examples7-13;

FIG. 12 is a line graph graphically representing differences in theBrookfield Viscosity (measured at 300° F. (149° C.)) of vacuum residueproducts having a boiling point of 1000° F.+(538° C.+) produced whenhydroprocessing Arab Medium heavy oil feedstock using differentdispersed metal sulfide catalyst particle concentrations and atdifferent resid conversions according to Examples 7-13;

FIG. 13 is a line graph graphically representing differences in the °API Gravity of vacuum residue products having a boiling point of 975°F.+(524° C.+) produced when hydroprocessing a heavy oil feedstock(Athabasca vacuum residuum) using different dispersed metal sulfidecatalyst particle concentrations and at different resid conversionsaccording to Examples 14-19;

FIG. 14 is a line graph graphically representing differences in thesulfur content of vacuum residue products having a boiling point of 975°F.+(524° C.+) produced when hydroprocessing Athabasca heavy oilfeedstock using different dispersed metal sulfide catalyst particleconcentrations and at different resid conversions according to Examples14-19;

FIG. 15 is a line graph graphically representing differences in theBrookfield Viscosity (measured at 300° F. (149° C.)) of vacuum residueproducts having a boiling point of 975° F.+(524° C.+) produced whenhydroprocessing Athabasca heavy oil feedstock using different dispersedmetal sulfide catalyst particle concentrations and at different residconversions according to Examples 16-19;

FIG. 16 is a line graph graphically representing differences in theheptane insoluble content of vacuum residue products having a boilingpoint of 975° F.+(524° C.+) produced when hydroprocessing Athabascaheavy oil feedstock using different dispersed metal sulfide catalystparticle concentrations and at different resid conversions according toExamples 16-19; and

FIG. 17 is a line graph graphically representing differences in thecarbon residue (MCR) content of vacuum residue products having a boilingpoint of 975° F.+(524° C.+) produced when hydroprocessing Athabascaheavy oil feedstock using different dispersed metal sulfide catalystparticle concentrations and at different resid conversions according toExamples 16-19.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction andDefinitions

The present invention relates to methods and systems for using a dualcatalyst system in an ebullated bed hydroprocessing system to produceconverted hydrocarbon products from heavy oil and also vacuum residueproducts of improved quality. The methods and systems involve the use ofa dual catalyst system comprised of a solid supported (i.e.,heterogeneous) catalyst and well-dispersed (e.g., homogeneous) catalystparticles. The dual catalyst system can be employed to upgrade anebullated bed hydroprocessing system that otherwise utilizes a singlecatalyst composed of a solid supported ebullated bed catalyst.

By way of example, a method of upgrading an ebullated bedhydroprocessing system to produce converted products from heavy oil,including vacuum residue products of improved quality, comprises: (1)operating an ebullated bed reactor using a heterogeneous catalyst tohydroprocess heavy oil and produce converted products, including avacuum residue product of initial quality; (2) thereafter upgrading theebullated bed reactor to operate using a dual catalyst system comprisedof dispersed metal sulfide catalyst particles and heterogeneouscatalyst; and (3) operating the upgraded ebullated bed reactor toproduce converted products, including a vacuum residue product ofimproved quality than when initially operating the ebullated bedreactor.

The term “heavy oil feedstock” shall refer to heavy crude, oil sandsbitumen, bottom of the barrel and residuum left over from refineryprocesses (e.g., visbreaker bottoms), and any other lower qualitymaterials that contain a substantial quantity of high boilinghydrocarbon fractions and/or that include a significant quantity ofasphaltenes that can deactivate a heterogeneous catalyst and/or cause orresult in the formation of coke precursors and sediment. Examples ofheavy oil feedstocks include, but are not limited to, Lloydminster heavyoil, Cold Lake bitumen, Athabasca bitumen, atmospheric tower bottoms,vacuum tower bottoms, residuum (or “resid”), resid pitch, vacuum residue(e.g., Ural VR, Arab Medium VR, Athabasca VR, Cold Lake VR, Maya VR, andChichimene VR), deasphalted liquids obtained by solvent deasphalting,asphaltene liquids obtained as a byproduct of deasphalting, andnonvolatile liquid fractions that remain after subjecting crude oil,bitumen from tar sands, liquefied coal, oil shale, or coal tarfeedstocks to distillation, hot separation, solvent extraction, and thelike. By way of further example, atmospheric tower bottoms (ATB) canhave a nominal boiling point of at least 343° C. (650° F.) although itis understood that the cut point can vary among refineries and be ashigh as 380° C. (716° F.). Vacuum tower bottoms can have a nominalboiling point of at least 524° C. (975° F.), although it is understoodthat the cut point can vary among refineries and be as high as 538° C.(1000° F.) or even 565° C. (1050° F.).

The terms “asphaltene” and “asphaltenes” shall refer to materials in aheavy oil feedstock that are typically insoluble in paraffinic solventssuch as propane, butane, pentane, hexane, and heptane. Asphaltenes caninclude sheets of condensed ring compounds held together by heteroatomssuch as sulfur, nitrogen, oxygen and metals. Asphaltenes broadly includea wide range of complex compounds having anywhere from 80 to 1200 carbonatoms, with predominating molecular weights, as determined by solutiontechniques, in the 1200 to 16,900 range. About 80-90% of the metals inthe crude oil are contained in the asphaltene fraction which, togetherwith a higher concentration of non-metallic heteroatoms, renders theasphaltene molecules more hydrophilic and less hydrophobic than otherhydrocarbons in crude. A hypothetical asphaltene molecule structuredeveloped by A.G. Bridge and co-workers at Chevron is depicted inFIG. 1. Generally, asphaltenes are typically defined based on theresults of insolubles methods, and more than one definition ofasphaltenes may be used. Specifically, a commonly used definition ofasphaltenes is heptane insolubles minus toluene insolubles (i.e.,asphaltenes are soluble in toluene; sediments and residues insoluble intoluene are not counted as asphaltenes). Asphaltenes defined in thisfashion may be referred to as “C₇ asphaltenes”. However, an alternatedefinition may also be used with equal validity, measured as pentaneinsolubles minus toluene insolubles, and commonly referred to as “C₅asphaltenes”. In the examples of the present invention, the C₇asphaltene definition is used, but the C₅ asphaltene definition can bereadily substituted.

The terms “hydrocracking” and “hydroconversion” shall refer to a processwhose primary purpose is to reduce the boiling range of a heavy oilfeedstock and in which a substantial portion of the feedstock isconverted into products with boiling ranges lower than that of theoriginal feedstock. Hydrocracking or hydroconversion generally involvesfragmentation of larger hydrocarbon molecules into smaller molecularfragments having a fewer number of carbon atoms and a higherhydrogen-to-carbon ratio. The mechanism by which hydrocracking occurstypically involves the formation of hydrocarbon free radicals duringthermal fragmentation, followed by capping of the free radical ends ormoieties with hydrogen. The hydrogen atoms or radicals that react withhydrocarbon free radicals during hydrocracking can be generated at or byactive catalyst sites.

The term “hydrotreating” shall refer to operations whose primary purposeis to remove impurities such as sulfur, nitrogen, oxygen, halides, andtrace metals from the feedstock and saturate olefins and/or stabilizehydrocarbon free radicals by reacting them with hydrogen rather thanallowing them to react with themselves. The primary purpose is not tochange the boiling range of the feedstock. Hydrotreating is most oftencarried out using a fixed bed reactor, although other hydroprocessingreactors can also be used for hydrotreating, an example of which is anebullated bed hydrotreater.

Of course, “hydrocracking” or “hydroconversion” may also involve theremoval of sulfur and nitrogen from a feedstock as well as olefinsaturation and other reactions typically associated with“hydrotreating”. The terms “hydroprocessing” and “hydroconversion” shallbroadly refer to both “hydrocracking” and “hydrotreating” processes,which define opposite ends of a spectrum, and everything in betweenalong the spectrum.

The term “hydrocracking reactor” shall refer to any vessel in whichhydrocracking (i.e., reducing the boiling range) of a feedstock in thepresence of hydrogen and a hydrocracking catalyst is the primarypurpose. Hydrocracking reactors are characterized as having an inletport into which a heavy oil feedstock and hydrogen can be introduced, anoutlet port from which an upgraded feedstock or material can bewithdrawn, and sufficient thermal energy so as to form hydrocarbon freeradicals in order to cause fragmentation of larger hydrocarbon moleculesinto smaller molecules. Examples of hydrocracking reactors include, butare not limited to, slurry phase reactors (i.e., a two phase, gas-liquidsystem), ebullated bed reactors (i.e., a three phase, gas-liquid-solidsystem), fixed bed reactors (i.e., a three-phase system that includes aliquid feed trickling downward over or flowing upward through a fixedbed of solid heterogeneous catalyst with hydrogen typically flowingcocurrently, but possibly countercurrently, to the heavy oil).

The term “hydrocracking temperature” shall refer to a minimumtemperature required to cause significant hydrocracking of a heavy oilfeedstock. In general, hydrocracking temperatures will preferably fallwithin a range of about 399° C. (750° F.) to about 460° C. (860° F.),more preferably in a range of about 418° C. (785° F.) to about 443° C.(830° F.), and most preferably in a range of about 421° C. (790° F.) toabout 440° C. (825° F.).

The term “gas-liquid slurry phase hydrocracking reactor” shall refer toa hydroprocessing reactor that includes a continuous liquid phase and agaseous dispersed phase which forms a “slurry” of gaseous bubbles withinthe liquid phase. The liquid phase typically comprises a hydrocarbonfeedstock that may contain a low concentration of dispersed metalsulfide catalyst particles, and the gaseous phase typically compriseshydrogen gas, hydrogen sulfide, and vaporized low boiling pointhydrocarbon products. The liquid phase can optionally include a hydrogendonor solvent. The term “gas-liquid-solid, 3-phase slurry hydrocrackingreactor” is used when a solid catalyst is employed along with liquid andgas. The gas may contain hydrogen, hydrogen sulfide and vaporized lowboiling hydrocarbon products. The term “slurry phase reactor” shallbroadly refer to both type of reactors (e.g., those with dispersed metalsulfide catalyst particles, those with a micron-sized or largerparticulate catalyst, and those that include both).

The terms “solid heterogeneous catalyst”, “heterogeneous catalyst” and“supported catalyst” shall refer to catalysts typically used inebullated bed and fixed bed hydroprocessing systems, including catalystsdesigned primarily for hydrocracking, hydroconversion,hydrodemetallization, and/or hydrotreating. A heterogeneous catalysttypically comprises: (i) a catalyst support having a large surface areaand interconnected channels or pores; and (ii) fine active catalystparticles, such as sulfides of cobalt, nickel, tungsten, and molybdenumdispersed within the channels or pores. The pores of the support aretypically of limited size to maintain mechanical integrity of theheterogeneous catalyst and prevent breakdown and formation of excessivefines in the reactor. Heterogeneous catalysts can be produced ascylindrical pellets, cylindrical extrudates, other shapes such astrilobes, rings, saddles, or the like, or spherical solids.

The terms “dispersed metal sulfide catalyst particles” and “dispersedcatalyst” shall refer to catalyst particles having a particle size thatis less than 1 μm e.g., less than about 500 nm in diameter, or less thanabout 250 nm in diameter, or less than about 100 nm in diameter, or lessthan about 50 nm in diameter, or less than about 25 nm in diameter, orless than about 10 nm in diameter, or less than about 5 nm in diameter.The term “dispersed metal sulfide catalyst particles” may includemolecular or molecularly-dispersed catalyst compounds. The term“dispersed metal sulfide catalyst particles” excludes metal sulfideparticles and agglomerates of metal sulfide particles that are largerthan 1 μm.

The term “molecularly-dispersed catalyst” shall refer to catalystcompounds that are essentially “dissolved” or dissociated from othercatalyst compounds or molecules in a hydrocarbon feedstock or suitablediluent. It can include very small catalyst particles that contain a fewcatalyst molecules joined together (e.g., 15 molecules or less).

The term “residual catalyst particles” shall refer to catalyst particlesthat remain with an upgraded material when transferred from one vesselto another (e.g., from a hydroprocessing reactor to a separator and/orother hydroprocessing reactor).

The term “conditioned feedstock” shall refer to a hydrocarbon feedstockinto which a catalyst precursor has been combined and mixed sufficientlyso that, upon decomposition of the catalyst precursor and formation ofthe active catalyst, the catalyst will comprise dispersed metal sulfidecatalyst particles formed in situ within the feedstock.

The terms “upgrade”, “upgrading” and “upgraded”, when used to describe afeedstock that is being or has been subjected to hydroprocessing, or aresulting material or product, shall refer to one or more of a reductionin the molecular weight of the feedstock, a reduction in the boilingpoint range of the feedstock, a reduction in the specific gravity of thefeedstock, a reduction in the concentration of asphaltenes, a reductionin the concentration of hydrocarbon free radicals, and/or a reduction inthe quantity of impurities, such as sulfur, nitrogen, oxygen, halides,and/or metals.

The term “severity” generally refers to the amount of energy that isintroduced into heavy oil during hydroprocessing and is often related tothe operating temperature of the hydroprocessing reactor (i.e., highertemperature is related to higher severity; lower temperature is relatedto lower severity) in combination with the duration of said temperatureexposure. Increased severity generally increases the quantity ofconversion products produced by the hydroprocessing reactor, includingboth desirable products and undesirable conversion products. Desirableconversion products include hydrocarbons of reduced molecular weight,boiling point, and specific gravity, which can include end products suchas naphtha, diesel, jet fuel, kerosene, wax, fuel oil, and the like.Other desirable conversion products include higher boiling hydrocarbonsthat can be further processed using conventional refining and/ordistillation processes. Undesirable conversion products include coke,sediment, metals, and other solid materials that can deposit onhydroprocessing equipment and cause fouling, such as interior componentsof reactors, separators, filters, pipes, towers, heat exchangers, andthe heterogeneous catalyst. Undesirable conversion products can alsorefer to unconverted resid that remains after distillation, such asatmospheric tower bottoms (“ATB”) or vacuum tower bottoms (“VTB”).Minimizing undesirable conversion products reduces equipment fouling andshutdowns required to clean the equipment. Nevertheless, there may be adesirable amount of unconverted resid in order for downstream separationequipment to function properly and/or in order to provide a liquidtransport medium for containing coke, sediment, metals, and other solidmaterials that might otherwise deposit on and foul equipment but thatcan be transported away by the remaining resid.

Unconverted residues can also be useful products, such as fuel oil andasphalt for building roads. When residues are used for fuel oil, thequality of the fuel can be measured by one or more properties such asviscosity, specific gravity, asphaltene content, carbon content, sulfurcontent, and sediment, with lower values of each generally correspondingto higher quality fuel oil. For example, a vacuum residue designated foruse as fuel oil will be of higher quality when the viscosity is lower(e.g., because it will require less cutter stock (e.g., vacuum gas oilor cycle oil) in order to flow and be handled). Similarly, a reductionin the sulfur content of vacuum residue requires less dilution usinghigher value cutter stocks to meet specifications for maximum sulfurcontent. Reductions in asphaltene, sediment, and/or carbon content canimprove stability of the fuel oil.

In addition to temperature, “severity” can be related to one or both of“conversion” and “throughput”. Whether increased severity involvesincreased conversion and/or increased or decreased throughput may dependon the quality of the heavy oil feedstock and/or the mass balance of theoverall hydroprocessing system. For example, where it is desired toconvert a greater quantity of feed material and/or provide a greaterquantity of material to downstream equipment, increased severity mayprimarily involve increased throughput without necessarily increasingfractional conversion. This can include the case where resid fractions(ATB and/or VTB) are sold as fuel oil and increased conversion withoutincreased throughput might decrease the quantity of this product. In thecase where it is desired to increase the ratio of upgraded materials toresid fractions, it may be desirable to primarily increase conversionwithout necessarily increasing throughput. Where the quality of heavyoil introduced into the hydroprocessing reactor fluctuates, it may bedesirable to selectively increase or decrease one or both of conversionand throughput to maintain a desired ratio of upgraded materials toresid fractions and/or a desired absolute quantity or quantities of endproduct(s) being produced.

The terms “conversion” and “fractional conversion” refer to theproportion, often expressed as a percentage, of heavy oil that isbeneficially converted into lower boiling and/or lower molecular weightmaterials. The conversion is expressed as a percentage of the initialresid content (i.e. components with boiling point greater than a definedresidue cut point) which is converted to products with boiling pointless than the defined cut point. The definition of residue cut point canvary, and can nominally include 524° C. (975° F.), 538° C. (1000° F.),565° C. (1050° F.), and the like. It can be measured by distillationanalysis of feed and product streams to determine the concentration ofcomponents with boiling point greater than the defined cut point.Fractional conversion is expressed as (F−P)/F, where F is the quantityof resid in the combined feed streams, and P is the quantity in thecombined product streams, where both feed and product resid content arebased on the same cut point definition. The quantity of resid is mostoften defined based on the mass of components with boiling point greaterthan the defined cut point, but volumetric or molar definitions couldalso be used.

The term “throughput” refers to the quantity of feed material that isintroduced into the hydroprocessing reactor as a function of time. It isalso related to the total quantity of conversion products removed fromthe hydroprocessing reactor, including the combined amounts of desirableand undesirable products. Throughput can be expressed in volumetricterms, such as barrels per day, or in mass terms, such as metric tonsper hour. In common usage, throughput is defined as the mass orvolumetric feed rate of only the heavy oil feedstock itself (forexample, vacuum tower bottoms or the like). The definition does notnormally include quantities of diluents or other components that maysometimes be included in the overall feeds to a hydroconversion unit,although a definition which includes those other components could alsobe used.

The term “sediment” refers to solids formed in a liquid stream that cansettle out. Sediments can include inorganics, coke, or insolubleasphaltenes that precipitate after conversion. Sediment in petroleumproducts is commonly measured using the IP-375 hot filtration testprocedure for total sediment in residual fuel oils published as part ofISO 10307 and ASTM D4870. Other tests include the IP-390 sediment testand the Shell hot filtration test. Sediment is related to components ofthe oil that have a propensity for forming solids during processing andhandling. These solid-forming components have multiple undesirableeffects in a hydroconversion process, including degradation of productquality and operability problems related to equipment fouling. It shouldbe noted that although the strict definition of sediment is based on themeasurement of solids in a sediment test, it is common for the term tobe used more loosely to refer to the solids-forming components of theoil itself, which may not be present in the oil as actual solids, butwhich contribute to solids formation under certain conditions.

The term “fouling” refers to the formation of an undesirable phase(foulant) that interferes with processing. The foulant is normally acarbonaceous material or solid that deposits and collects within theprocessing equipment. Equipment fouling can result in loss of productiondue to equipment shutdown, decreased performance of equipment, increasedenergy consumption due to the insulating effect of foulant deposits inheat exchangers or heaters, increased maintenance costs for equipmentcleaning, reduced efficiency of fractionators, and reduced reactivity ofheterogeneous catalyst.

II. Ebullated Bed Hydroprocessing Reactors and Systems

FIGS. 2A-2D schematically depict non-limiting examples of ebullated bedhydroprocessing reactors and systems used to hydroprocess hydrocarbonfeedstocks such as heavy oil, which can be upgraded to use a dualcatalyst system according to the invention. It will be appreciated thatthe example ebullated bed hydroprocessing reactors and systems caninclude interstage separation, integrated hydrotreating, and/orintegrated hydrocracking.

FIG. 2A schematically illustrates an ebullated bed hydroprocessingreactor 10 used in the LC-Fining hydrocracking system developed by C-ELummus. Ebullated bed reactor 10 includes an inlet port 12 near thebottom, through which a feedstock 14 and pressurized hydrogen gas 16 areintroduced, and an outlet port 18 at the top, through whichhydroprocessed material 20 is withdrawn.

Reactor 10 further includes an expanded catalyst zone 22 comprising aheterogeneous catalyst 24 that is maintained in an expanded or fluidizedstate against the force of gravity by upward movement of liquidhydrocarbons and gas (schematically depicted as bubbles 25) throughebullated bed reactor 10. The lower end of expanded catalyst zone 22 isdefined by a distributor grid plate 26, which separates expandedcatalyst zone 22 from a lower heterogeneous catalyst free zone 28located between the bottom of ebullated bed reactor 10 and distributorgrid plate 26. Distributor grid plate 26 is configured to distribute thehydrogen gas and hydrocarbons evenly across the reactor and preventsheterogeneous catalyst 24 from falling by the force of gravity intolower heterogeneous catalyst free zone 28. The upper end of the expandedcatalyst zone 22 is the height at which the downward force of gravitybegins to equal or exceed the uplifting force of the upwardly movingfeedstock and gas through ebullated bed reactor 10 as heterogeneouscatalyst 24 reaches a given level of expansion or separation. Aboveexpanded catalyst zone 22 is an upper heterogeneous catalyst free zone30.

Hydrocarbons and other materials within the ebullated bed reactor 10 arecontinuously recirculated from upper heterogeneous catalyst free zone 30to lower heterogeneous catalyst free zone 28 by means of a recyclingchannel 32 positioned in the center of ebullated bed reactor 10connected to an ebullating pump 34 at the bottom of ebullated bedreactor 10. At the top of recycling channel 32 is a funnel-shapedrecycle cup 36 through which feedstock is drawn from upper heterogeneouscatalyst free zone 30. Material drawn downward through recycling channel32 enters lower catalyst free zone 28 and then passes upwardly throughdistributor grid plate 26 and into expanded catalyst zone 22, where itis blended with freshly added feedstock 14 and hydrogen gas 16 enteringebullated bed reactor 10 through inlet port 12. Continuously circulatingblended materials upward through the ebullated bed reactor 10advantageously maintains heterogeneous catalyst 24 in an expanded orfluidized state within expanded catalyst zone 22, minimizes channeling,controls reaction rates, and keeps heat released by the exothermichydrogenation reactions to a safe level.

Fresh heterogeneous catalyst 24 is introduced into ebullated bed reactor10, such as expanded catalyst zone 22, through a catalyst inlet tube 38,which passes through the top of ebullated bed reactor 10 and directlyinto expanded catalyst zone 22. Spent heterogeneous catalyst 24 iswithdrawn from expanded catalyst zone 22 through a catalyst withdrawaltube 40 that passes from a lower end of expanded catalyst zone 22through distributor grid plate 26 and the bottom of ebullated bedreactor 10. It will be appreciated that the catalyst withdrawal tube 40is unable to differentiate between fully spent catalyst, partially spentbut active catalyst, and freshly added catalyst such that a randomdistribution of heterogeneous catalyst 24 is typically withdrawn fromebullated bed reactor 10 as “spent” catalyst.

Upgraded material 20 withdrawn from ebullated bed reactor 10 can beintroduced into a separator 42 (e.g., hot separator, inter-stagepressure differential separator, or distillation tower, such asatmospheric or vacuum). The separator 42 separates one or more volatilefractions 46 from a non-volatile fraction 48.

FIG. 2B schematically illustrates an ebullated bed reactor 110 used inthe H-Oil hydrocracking system developed by Hydrocarbon ResearchIncorporated and currently licensed by Axens. Ebullated bed reactor 110includes an inlet port 112, through which a heavy oil feedstock 114 andpressurized hydrogen gas 116 are introduced, and an outlet port 118,through which upgraded material 120 is withdrawn. An expanded catalystzone 122 comprising a heterogeneous catalyst 124 is bounded by adistributor grid plate 126, which separates expanded catalyst zone 122from a lower catalyst free zone 128 between the bottom of reactor 110and distributor grid plate 126, and an upper end 129, which defines anapproximate boundary between expanded catalyst zone 122 and an uppercatalyst free zone 130. Dotted boundary line 131 schematicallyillustrates the approximate level of heterogeneous catalyst 124 when notin an expanded or fluidized state.

Materials are continuously recirculated within reactor 110 by arecycling channel 132 connected to an ebullating pump 134 positionedoutside of reactor 110. Materials are drawn through a funnel-shapedrecycle cup 136 from upper catalyst free zone 130. Recycle cup 136 isspiral-shaped, which helps separate hydrogen bubbles 125 from recyclesmaterial 132 to prevent cavitation of ebullating pump 134. Recycledmaterial 132 enters lower catalyst free zone 128, where it is blendedwith fresh feedstock 116 and hydrogen gas 118, and the mixture passes upthrough distributor grid plate 126 and into expanded catalyst zone 122.Fresh catalyst 124 is introduced into expanded catalyst zone 122 througha catalyst inlet tube 136, and spent catalyst 124 is withdrawn fromexpanded catalyst zone 122 through a catalyst discharge tube 140.

The main difference between the H-Oil ebullated bed reactor 110 and theLC-Fining ebullated bed reactor 10 is the location of the ebullatingpump. Ebullating pump 134 in H-Oil reactor 110 is located external tothe reaction chamber. The recirculating feedstock is introduced througha recirculation port 141 at the bottom of reactor 110. The recirculationport 141 includes a distributor 143, which aids in evenly distributingmaterials through lower catalyst free zone 128. Upgraded material 120 isshown being sent to a separator 142, which separates one or morevolatile fractions 146 from a non-volatile fraction 148.

FIG. 2C schematically illustrates an ebullated bed hydroprocessingsystem 200 comprising multiple ebullated bed reactors. Hydroprocessingsystem 200, an example of which is an LC-Fining hydroprocessing unit,may include three ebullated bed reactors 210 in series for upgrading afeedstock 214. Feedstock 214 is introduced into a first ebullated bedreactor 210 a together with hydrogen gas 216, both of which are passedthrough respective heaters prior to entering the reactor. Upgradedmaterial 220 a from first ebullated bed reactor 210 a is introducedtogether with additional hydrogen gas 216 into a second ebullated bedreactor 210 b. Upgraded material 220 b from second ebullated bed reactor210 b is introduced together with additional hydrogen gas 216 into athird ebullated bed reactor 210 c.

It should be understood that one or more interstage separators canoptionally be interposed between first and second reactors 210 a, 210 band/or second and third reactors 210 b, 210 c, in order to remove lowerboiling fractions and gases from a non-volatile fraction containingliquid hydrocarbons and residual dispersed metal sulfide catalystparticles. It can be desirable to remove lower alkanes, such as hexanesand heptanes, which are valuable fuel products but poor solvents forasphaltenes. Removing volatile materials between multiple reactorsenhances production of valuable products and increases the solubility ofasphaltenes in the hydrocarbon liquid fraction fed to the downstreamreactor(s). Both increase efficiency of the overall hydroprocessingsystem.

Upgraded material 220 c from third ebullated bed reactor 210 c is sentto a high temperature separator 242 a, which separates volatile andnon-volatile fractions. Volatile fraction 246 a passes through a heatexchanger 250, which preheats hydrogen gas 216 prior to being introducedinto first ebullated bed reactor 210 a. The somewhat cooled volatilefraction 246 a is sent to a medium temperature separator 242 b, whichseparates a remaining volatile fraction 246 b from a resulting liquidfraction 248 b that forms as a result of cooling by heat exchanger 250.Remaining volatile fraction 246 b is sent downstream to a lowtemperature separator 246 c for further separation into a gaseousfraction 252 c and a degassed liquid fraction 248 c.

A liquid fraction 248 a from high temperature separator 242 a is senttogether with resulting liquid fraction 248 b from medium temperatureseparator 242 b to a low pressure separator 242 d, which separates ahydrogen rich gas 252 d from a degassed liquid fraction 248 d, which isthen mixed with the degassed liquid fraction 248 c from low temperatureseparator 242 c and fractionated into products. Gaseous fraction 252 cfrom low temperature separator 242 c is purified into off gas, purgegas, and hydrogen gas 216. Hydrogen gas 216 is compressed, mixed withmake-up hydrogen gas 216 a, and either passed through heat exchanger 250and introduced into first ebullated bed reactor 210 a together withfeedstock 216 or introduced directly into second and third ebullated bedreactors 210 b and 210 b.

FIG. 2D schematically illustrates an ebullated bed hydroprocessingsystem 200 comprising multiple ebullated bed reactors, similar to thesystem illustrated in FIG. 2C, but showing an interstage separator 221interposed between second and third reactors 210 b, 210 c (althoughinterstage separator 221 may be interposed between first and secondreactors 210 a, 210 b). As illustrated, the effluent from second-stagereactor 210 b enters interstage separator 221, which can be ahigh-pressure, high-temperature separator. The liquid fraction fromseparator 221 is combined with a portion of the recycle hydrogen fromline 216 and then enters third-stage reactor 210 c. The vapor fractionfrom the interstage separator 221 bypasses third-stage reactor 210 c,mixes with effluent from third-stage reactor 210 c, and then passes intoa high-pressure, high-temperature separator 242 a.

This allows lighter, more-saturated components formed in the first tworeactor stages to bypass third-stage reactor 210 c. The benefits of thisare (1) a reduced vapor load on the third-stage reactor, which increasesthe volume utilization of the third-stage reactor for converting theremaining heavy components, and (2) a reduced concentration of“anti-solvent” components (saturates) which can destabilize asphaltenesin third-stage reactor 210 c.

In preferred embodiments, the hydroprocessing systems are configured andoperated to promote hydrocracking reactions rather than merehydrotreating, which is a less severe form of hydroprocessing.Hydrocracking involves the breaking of carbon-carbon molecular bonds,such as reducing the molecular weight of larger hydrocarbon moleculesand/or ring opening of aromatic compounds. Hydrotreating, on the otherhand, mainly involves hydrogenation of unsaturated hydrocarbons, withminimal or no breaking of carbon-carbon molecular bonds. To promotehydrocracking rather than mere hydrotreating reactions, thehydroprocessing reactor(s) are preferably operated at a temperature in arange of about 750° F. (399° C.) to about 860° F. (460° C.), morepreferably in a range of about 780° F. (416° C.) to about 830° F. (443°C.), are preferably operated at a pressure in a range of about 1000 psig(6.9 MPa) to about 3000 psig (20.7 MPa), more preferably in a range ofabout 1500 psig (10.3 MPa) to about 2500 psig (17.2 MPa), and arepreferably operated at a space velocity (e.g., Liquid Hourly SpaceVelocity, or LHSV, defined as the ratio of feed volume to reactor volumeper hour) in a range of about 0.05 hr⁻¹ to about 0.45 hr⁻¹, morepreferably in a range of about 0.15 hr⁻¹ to about 0.35 hr⁻¹. Thedifference between hydrocracking and hydrotreating can also be expressedin terms of resid conversion (wherein hydrocracking results in thesubstantial conversion of higher boiling to lower boiling hydrocarbons,while hydrotreating does not). The hydroprocessing systems disclosedherein can result in a resid conversion in a range of about 40% to about90%, preferably in a range of about 55% to about 80%. The preferredconversion range typically depends on the type of feedstock because ofdifferences in processing difficulty between different feedstocks.Typically, conversion will be at least about 5% higher, preferably atleast about 10% higher, compared to operating an ebullated bed reactorprior to upgrading to utilize a dual catalyst system as disclosedherein.

III. Upgrading an Ebullated Bed Hydroprocessing Reactor

FIGS. 3A, 3B, 3C, and 3D are flow diagrams which illustrate exemplarymethods for upgrading an ebullated bed reactor to use a dual catalystsystem and produce vacuum residue products of improved quality (e.g., asmeasured by one or more of reduced viscosity, reduced specific gravity,reduced asphaltene content, reduced carbon content, reduced sulfurcontent, and reduced sediment content).

FIG. 3A is a flow diagram that illustrates a method comprising: (1)initially operating an ebullated bed reactor to hydroprocess heavy oilusing a heterogeneous catalyst at initial conditions and producingvacuum residue of initial quality; (2) adding dispersed metal sulfidecatalyst particles to the ebullated bed reactor to form an upgradedreactor with a dual catalyst system including a heterogeneous catalystand the dispersed metal sulfide catalyst particles; and (3) operatingthe upgraded ebullated bed reactor using the dual catalyst system atsimilar or higher severity and producing a vacuum residue product ofimproved quality than when operating at the initial conditions.

According to some embodiments, the heterogeneous catalyst utilized wheninitially operating the ebullated bed reactor at an initial condition isa commercially available catalyst that is typically used in ebullatedbed reactors. To maximize efficiency, the initial reactor conditions mayadvantageously be at a reactor severity at which sediment formation andfouling are maintained within acceptable levels. Increasing reactorseverity without upgrading the ebullated reactor to use a dual catalystsystem may therefore result in excessive sediment formation andundesirable equipment fouling, which would otherwise require morefrequent shutdown and cleaning of the hydroprocessing reactor andrelated equipment, such as pipes, towers, heaters, heterogeneouscatalyst and/or separation equipment.

In order to improve the quality of vacuum residue produced whileoperating the ebullated bed reactor at similar or increased severity,the ebullated bed reactor is upgraded to use a dual catalyst systemcomprising a heterogeneous catalyst and dispersed metal sulfide catalystparticles. Vacuum residue products of improved quality are characterizedby one or more of reduced viscosity, reduced specific gravity, reducedasphaltene content, reduced carbon content, reduced sulfur content, andreduced sediment.

FIG. 3B is a flow diagram that illustrates a method comprising: (1)initially operating an ebullated bed reactor to hydroprocess heavy oilusing a heterogeneous catalyst at initial conditions and producingvacuum residue of initial quality; (2) adding dispersed metal sulfidecatalyst particles to the ebullated bed reactor to form an upgradedreactor with a dual catalyst system including a heterogeneous catalystand the dispersed metal sulfide catalyst particles; and (3) operatingthe upgraded ebullated bed reactor using the dual catalyst system atsimilar or higher throughput and producing a vacuum residue product ofimproved quality than when operating at the initial conditions.

FIG. 3C is a flow diagram that illustrates a method comprising: (1)initially operating an ebullated bed reactor to hydroprocess heavy oilusing a heterogeneous catalyst at initial conditions and producingvacuum residue of initial quality; (2) adding dispersed metal sulfidecatalyst particles to the ebullated bed reactor to form an upgradedreactor with a dual catalyst system including a heterogeneous catalystand the dispersed metal sulfide catalyst particles; and (3) operatingthe upgraded ebullated bed reactor using the dual catalyst system atsimilar or higher conversion and producing a vacuum residue product ofimproved quality than when operating at the initial conditions.

FIG. 3D is a flow diagram that illustrates a method comprising: (1)initially operating an ebullated bed reactor to hydroprocess heavy oilusing a heterogeneous catalyst at initial conditions and producingvacuum residue of initial quality; (2) adding dispersed metal sulfidecatalyst particles to the ebullated bed reactor to form an upgradedreactor with a dual catalyst system including a heterogeneous catalystand the dispersed metal sulfide catalyst particles; and (3) operatingthe upgraded ebullated bed reactor using the dual catalyst system athigher severity, throughput and/or conversion and producing a vacuumresidue product of same or improved quality than when operating at theinitial conditions.

The dispersed metal sulfide catalyst particles can be generatedseparately and then added to the ebullated bed reactor when forming thedual catalyst system. Alternatively or in addition, at least a portionof the dispersed metal sulfide catalyst particles can be generated insitu in the heavy oil within the ebullated bed reactor.

In some embodiments, the dispersed metal sulfide catalyst particles areadvantageously formed in situ within an entirety of a heavy oilfeedstock. This can be accomplished by initially mixing a catalystprecursor with an entirety of the heavy oil feedstock to form aconditioned feedstock and thereafter heating the conditioned feedstockto decompose the catalyst precursor and cause or allow catalyst metal toreact with sulfur and/or sulfur-containing molecules in and/or added tothe heavy oil to form the dispersed metal sulfide catalyst particles.

The catalyst precursor can be oil soluble and have a decompositiontemperature in a range from about 100° C. (212° F.) to about 350° C.(662° F.), or in a range of about 150° C. (302° F.) to about 300° C.(572° F.), or in a range of about 175° C. (347° F.) to about 250° C.(482° F.). Example catalyst precursors include organometallic complexesor compounds, more specifically oil soluble compounds or complexes oftransition metals and organic acids, having a decomposition temperatureor range high enough to avoid substantial decomposition when mixed witha heavy oil feedstock under suitable mixing conditions. When mixing thecatalyst precursor with a hydrocarbon oil diluent, it is advantageous tomaintain the diluent at a temperature below which significantdecomposition of the catalyst precursor occurs. One of skill in the artcan, following the present disclosure, select a mixing temperatureprofile that results in intimate mixing of a selected precursorcomposition without substantial decomposition prior to formation of thedispersed metal sulfide catalyst particles.

Example catalyst precursors include, but are not limited to, molybdenum2-ethylhexanoate, molybdenum octoate, molybdenum naphthanate, vanadiumnaphthanate, vanadium octoate, molybdenum hexacarbonyl, vanadiumhexacarbonyl, and iron pentacarbonyl. Other catalyst precursors includemolybdenum salts comprising a plurality of cationic molybdenum atoms anda plurality of carboxylate anions of at least 8 carbon atoms and thatare at least one of (a) aromatic, (b) alicyclic, or (c) branched,unsaturated and aliphatic. By way of example, each carboxylate anion mayhave between 8 and 17 carbon atoms or between 11 and 15 carbon atoms.Examples of carboxylate anions that fit at least one of the foregoingcategories include carboxylate anions derived from carboxylic acidsselected from the group consisting of 3-cyclopentylpropionic acid,cyclohexanebutyric acid, biphenyl-2-carboxylic acid, 4-heptylbenzoicacid, 5-phenylvaleric acid, geranic acid (3,7-dimethyl-2,6-octadienoicacid), and combinations thereof.

In other embodiments, carboxylate anions for use in making oil soluble,thermally stable, molybdenum catalyst precursor compounds are derivedfrom carboxylic acids selected from the group consisting of3-cyclopentylpropionic acid, cyclohexanebutyric acid,biphenyl-2-carboxylic acid, 4-heptylbenzoic acid, 5-phenylvaleric acid,geranic acid (3,7-dimethyl-2,6-octadienoic acid), 10-undecenoic acid,dodecanoic acid, and combinations thereof. It has been discovered thatmolybdenum catalyst precursors made using carboxylate anions derivedfrom the foregoing carboxylic acids possess improved thermal stability.

Catalyst precursors with higher thermal stability can have a firstdecomposition temperature higher than 210° C., higher than about 225°C., higher than about 230° C., higher than about 240° C., higher thanabout 275° C., or higher than about 290° C. Such catalyst precursors canhave a peak decomposition temperature higher than 250° C., or higherthan about 260° C., or higher than about 270° C., or higher than about280° C., or higher than about 290° C., or higher than about 330° C.

One of skill in the art can, following the present disclosure, select amixing temperature profile that results in intimate mixing of a selectedprecursor composition without substantial decomposition prior toformation of the dispersed metal sulfide catalyst particles.

Whereas it is within the scope of the invention to directly blend thecatalyst precursor composition with the heavy oil feedstock, care mustbe taken in such cases to mix the components for a time sufficient tothoroughly blend the precursor composition within the feedstock beforesubstantial decomposition of the precursor composition has occurred. Forexample, U.S. Pat. No. 5,578,197 to Cyr et al., the disclosure of whichis incorporated by reference, describes a method whereby molybdenum2-ethyl hexanoate was mixed with bitumen vacuum tower residuum for 24hours before the resulting mixture was heated in a reaction vessel toform the catalyst compound and to effect hydrocracking (see col. 10,lines 4-43). Whereas 24-hour mixing in a testing environment may beentirely acceptable, such long mixing times may make certain industrialoperations prohibitively expensive. To ensure thorough mixing of thecatalyst precursor within the heavy oil prior to heating to form theactive catalyst, a series of mixing steps are performed by differentmixing apparatus prior to heating the conditioned feedstock. These mayinclude one or more low shear in-line mixers, followed by one or morehigh shear mixers, followed by a surge vessel and pump-around system,followed by one or more multi-stage high pressure pumps used topressurize the feed stream prior to introducing it into ahydroprocessing reactor.

In some embodiments, the conditioned feedstock is pre-heated using aheating apparatus prior to entering the hydroprocessing reactor in orderto form at least a portion of the dispersed metal sulfide catalystparticles in situ within the heavy oil. In other embodiments, theconditioned feedstock is heated or further heated in the hydroprocessingreactor in order to form at least a portion of the dispersed metalsulfide catalyst particles in situ within the heavy oil.

In some embodiments, the dispersed metal sulfide catalyst particles canbe formed in a multi-step process. For example, an oil soluble catalystprecursor composition can be premixed with a hydrocarbon diluent to forma diluted precursor mixture. Examples of suitable hydrocarbon diluentsinclude, but are not limited to, vacuum gas oil (which typically has anominal boiling range of 360-524° C.) (680-975° F.), decant oil or cycleoil (which typically has a nominal boiling range of 360°-550° C.)(680-1022° F.), and gas oil (which typically has a nominal boiling rangeof 200°-360° C.) (392-680° F.), a portion of the heavy oil feedstock,and other hydrocarbons that nominally boil at a temperature higher thanabout 200° C.

The ratio of catalyst precursor to hydrocarbon oil diluent used to makethe diluted precursor mixture can be in a range of about 1:500 to about1:1, or in a range of about 1:150 to about 1:2, or in a range of about1:100 to about 1:5 (e.g., 1:100, 1:50, 1:30, or 1:10).

The amount of catalyst metal (e.g., molybdenum) in the diluted precursormixture is preferably in a range of about 100 ppm to about 7000 ppm byweight of the diluted precursor mixture, more preferably in a range ofabout 300 ppm to about 4000 ppm by weight of the diluted precursormixture.

The catalyst precursor is advantageously mixed with the hydrocarbondiluent below a temperature at which a significant portion of thecatalyst precursor composition decomposes. The mixing may be performedat temperature in a range of about 25° C. (77° F.) to about 250° C.(482° F.), or in range of about 50° C. (122° F.) to about 200° C. (392°F.), or in a range of about 75° C. (167° F.) to about 150° C. (302° F.),to form the diluted precursor mixture. The temperature at which thediluted precursor mixture is formed may depend on the decompositiontemperature and/or other characteristics of the catalyst precursor thatis utilized and/or characteristics of the hydrocarbon diluent, such asviscosity.

The catalyst precursor is preferably mixed with the hydrocarbon oildiluent for a time period in a range of about 0.1 second to about 5minutes, or in a range of about 0.5 second to about 3 minutes, or in arange of about 1 second to about 1 minute. The actual mixing time isdependent, at least in part, on the temperature (i.e., which affects theviscosity of the fluids) and mixing intensity. Mixing intensity isdependent, at least in part, on the number of stages e.g., for anin-line static mixer.

Pre-blending the catalyst precursor with a hydrocarbon diluent to form adiluted precursor mixture which is then blended with the heavy oilfeedstock greatly aids in thoroughly and intimately blending thecatalyst precursor within the feedstock, particularly in the relativelyshort period of time required for large-scale industrial operations.Forming a diluted precursor mixture shortens the overall mixing time by(1) reducing or eliminating differences in solubility between a morepolar catalyst precursor and a more hydrophobic heavy oil feedstock, (2)reducing or eliminating differences in rheology between the catalystprecursor and heavy oil feedstock, and/or (3) breaking up catalystprecursor molecules to form a solute within the hydrocarbon diluent thatis more easily dispersed within the heavy oil feedstock.

The diluted precursor mixture is then combined with the heavy oilfeedstock and mixed for a time sufficient and in a manner so as todisperse the catalyst precursor throughout the feedstock to form aconditioned feedstock in which the catalyst precursor is thoroughlymixed within the heavy oil prior to thermal decomposition and formationof the active metal sulfide catalyst particles. In order to obtainsufficient mixing of the catalyst precursor within the heavy oilfeedstock, the diluted precursor mixture and heavy oil feedstock areadvantageously mixed for a time period in a range of about 0.1 second toabout 5 minutes, or in a range from about 0.5 second to about 3 minutes,or in a range of about 1 second to about 3 minutes. Increasing thevigorousness and/or shearing energy of the mixing process generallyreduce the time required to effect thorough mixing.

Examples of mixing apparatus that can be used to effect thorough mixingof the catalyst precursor and/or diluted precursor mixture with heavyoil include, but are not limited to, high shear mixing such as mixingcreated in a vessel with a propeller or turbine impeller; multiplestatic in-line mixers; multiple static in-line mixers in combinationwith in-line high shear mixers; multiple static in-line mixers incombination with in-line high shear mixers followed by a surge vessel;combinations of the above followed by one or more multi-stagecentrifugal pumps; and one or more multi-stage centrifugal pumps.According some embodiments, continuous rather than batch-wise mixing canbe carried out using high energy pumps having multiple chambers withinwhich the catalyst precursor composition and heavy oil feedstock arechurned and mixed as part of the pumping process itself. The foregoingmixing apparatus may also be used for the pre-mixing process discussedabove in which the catalyst precursor is mixed with the hydrocarbondiluent to form the catalyst precursor mixture.

In the case of heavy oil feedstocks that are solid or extremely viscousat room temperature, such feedstocks may advantageously be heated inorder to soften them and create a feedstock having sufficiently lowviscosity so as to allow good mixing of the oil soluble catalystprecursor into the feedstock composition. In general, decreasing theviscosity of the heavy oil feedstock will reduce the time required toeffect thorough and intimate mixing of the oil soluble precursorcomposition within the feedstock.

The heavy oil feedstock and catalyst precursor and/or diluted precursormixture are advantageously mixed at a temperature in a range of about25° C. (77° F.) to about 350° C. (662° F.), or in a range of about 50°C. (122° F.) to about 300° C. (572° F.), or in a range of about 75° C.(167° F.) to about 250° C. (482° F.) to yield a conditioned feedstock.

In the case where the catalyst precursor is mixed directly with theheavy oil feedstock without first forming a diluted precursor mixture,it may be advantageous to mix the catalyst precursor and heavy oilfeedstock below a temperature at which a significant portion of thecatalyst precursor composition decomposes. However, in the case wherethe catalyst precursor is premixed with a hydrocarbon diluent to form adiluted precursor mixture, which is thereafter mixed with the heavy oilfeedstock, it may be permissible for the heavy oil feedstock to be at orabove the decomposition temperature of the catalyst precursor. That isbecause the hydrocarbon diluent shields the individual catalystprecursor molecules and prevents them from agglomerating to form largerparticles, temporarily insulates the catalyst precursor molecules fromheat from the heavy oil during mixing, and facilitates dispersion of thecatalyst precursor molecules sufficiently quickly throughout the heavyoil feedstock before decomposing to liberate metal. In addition,additional heating of the feedstock may be necessary to liberatehydrogen sulfide from sulfur-bearing molecules in the heavy oil to formthe metal sulfide catalyst particles. In this way, progressive dilutionof the catalyst precursor permits a high level of dispersion within theheavy oil feedstock, resulting in the formation of highly dispersedmetal sulfide catalyst particles, even where the feedstock is at atemperature above the decomposition temperature of the catalystprecursor.

After the catalyst precursor has been well-mixed throughout the heavyoil to yield a conditioned feedstock, this composition is then heated tocause decomposition of the catalyst precursor to liberate catalyst metaltherefrom, cause or allow it to react with sulfur within and/or added tothe heavy oil, and form the active metal sulfide catalyst particles.Metal from the catalyst precursor may initially form a metal oxide,which then reacts with sulfur in the heavy oil to yield a metal sulfidecompound that forms the final active catalyst. In the case where theheavy oil feedstock includes sufficient or excess sulfur, the finalactivated catalyst may be formed in situ by heating the heavy oilfeedstock to a temperature sufficient to liberate sulfur therefrom. Insome cases, sulfur may be liberated at the same temperature that theprecursor composition decomposes. In other cases, further heating to ahigher temperature may be required.

If the catalyst precursor is thoroughly mixed throughout the heavy oil,at least a substantial portion of the liberated metal ions will besufficiently sheltered or shielded from other metal ions so that theycan form a molecularly-dispersed catalyst upon reacting with sulfur toform the metal sulfide compound. Under some circumstances, minoragglomeration go may occur, yielding colloidal-sized catalyst particles.However, it is believed that taking care to thoroughly mix the catalystprecursor throughout the feedstock prior to thermal decomposition of thecatalyst precursor may yield individual catalyst molecules rather thancolloidal particles. Simply blending, while failing to sufficiently mix,the catalyst precursor with the feedstock typically causes formation oflarge agglomerated metal sulfide compounds that are micron-sized orlarger.

In order to form dispersed metal sulfide catalyst particles, theconditioned feedstock is heated to a temperature in a range of about275° C. (527° F.) to about 450° C. (842° F.), or in a range of about310° C. (590° F.) to about 430° C. (806° F.), or in a range of about330° C. (626° F.) to about 410° C. (770° F.).

The initial concentration of catalyst metal provided by dispersed metalsulfide catalyst particles can be in a range of about 1 ppm to about 500ppm by weight of the heavy oil feedstock, or in a range of about 5 ppmto about 300 ppm, or in a range of about 10 ppm to about 100 ppm. Thecatalyst may become more concentrated as volatile fractions are removedfrom a resid fraction.

In the case where the heavy oil feedstock includes a significantquantity of asphaltene molecules, the dispersed metal sulfide catalystparticles may preferentially associate with, or remain in closeproximity to, the asphaltene molecules. Asphaltene molecules can have agreater affinity for the metal sulfide catalyst particles sinceasphaltene molecules are generally more hydrophilic and less hydrophobicthan other hydrocarbons contained within heavy oil. Because the metalsulfide catalyst particles tend to be very hydrophilic, the individualparticles or molecules will tend to migrate toward more hydrophilicmoieties or molecules within the heavy oil feedstock.

While the highly polar nature of metal sulfide catalyst particles causesor allows them to associate with asphaltene molecules, it is the generalincompatibility between the highly polar catalyst compounds andhydrophobic heavy oil that necessitates the aforementioned intimate orthorough mixing of catalyst precursor composition within the heavy oilprior to decomposition and formation of the active catalyst particles.Because metal catalyst compounds are highly polar, they cannot beeffectively dispersed within heavy oil if added directly thereto. Inpractical terms, forming smaller active catalyst particles results in agreater number of catalyst particles that provide more evenlydistributed catalyst sites throughout the heavy oil.

IV. Upgraded Ebullated Bed Reactor

FIG. 4 schematically illustrates an example upgraded ebullated bedhydroprocessing system 400 that can be used in the disclosed methods andsystems. Ebullated bed hydroprocessing system 400 includes an upgradedebullated bed reactor 430 and a hot separator 404 (or other separator,such as a distillation tower). To create upgraded ebullated bed reactor430, a catalyst precursor 402 is initially pre-blended with ahydrocarbon diluent 404 in one or more mixers 406 to form a catalystprecursor mixture 409. Catalyst precursor mixture 409 is added tofeedstock 408 and blended with the feedstock in one or more mixers 410to form conditioned feedstock 411. Conditioned feedstock is fed to asurge vessel 412 with pump around 414 to cause further mixing anddispersion of the catalyst precursor within the conditioned feedstock.

The conditioned feedstock from surge vessel 412 is pressurized by one ormore pumps 416, passed through a pre-heater 418, and fed into ebullatedbed reactor 430 together with pressurized hydrogen gas 420 through aninlet port 436 located at or near the bottom of ebullated bed reactor430. Heavy oil material 426 in ebullated bed reactor 430 containsdispersed metal sulfide catalyst particles, schematically depicted ascatalyst particles 424.

Heavy oil feedstock 408 may comprise any desired fossil fuel feedstockand/or fraction thereof including, but not limited to, one or more ofheavy crude, oil sands bitumen, bottom of the barrel fractions fromcrude oil, atmospheric tower bottoms, vacuum tower bottoms, coal tar,liquefied coal, and other resid fractions. In some embodiments, heavyoil feedstock 408 can include a significant fraction of high boilingpoint hydrocarbons (i.e., nominally at or above 343° C. (650° F.), moreparticularly nominally at or above about 524° C. (975° F.)) and/orasphaltenes. Asphaltenes are complex hydrocarbon molecules that includea relatively low ratio of hydrogen to carbon that is the result of asubstantial number of condensed aromatic and naphthenic rings withparaffinic side chains (See FIG. 1). Sheets consisting of the condensedaromatic and naphthenic rings are held together by heteroatoms such assulfur or nitrogen and/or polymethylene bridges, thio-ether bonds, andvanadium and nickel complexes. The asphaltene fraction also contains ahigher content of sulfur and nitrogen than does crude oil or the rest ofthe vacuum resid, and it also contains higher concentrations ofcarbon-forming compounds (i.e., that form coke precursors and sediment).

Ebullated bed reactor 430 further includes an expanded catalyst zone 442comprising a heterogeneous catalyst 444. A lower heterogeneous catalystfree zone 448 is located below expanded catalyst zone 442, and an upperheterogeneous catalyst free zone 450 is located above expanded catalystzone 442. Dispersed metal sulfide catalyst particles 424 are dispersedthroughout material 426 within ebullated bed reactor 430, includingexpanded catalyst zone 442, heterogeneous catalyst free zones 448, 450,452 thereby being available to promote upgrading reactions within whatconstituted catalyst free zones in the ebullated bed reactor prior tobeing upgraded to include the dual catalyst system.

To promote hydrocracking rather than mere hydrotreating reactions, thehydroprocessing reactor(s) are preferably operated at a temperature in arange of about 750° F. (399° C.) to about 860° F. (460° C.), morepreferably in a range of about 780° F. (416° C.) to about 830° F. (443°C.), are preferably operated at a pressure in a range of about 1000 psig(6.9 MPa) to about 3000 psig (20.7 MPa), more preferably in a range ofabout 1500 psig (10.3 MPa) to about 2500 psig (17.2 MPa), and arepreferably operated at a space velocity (LHSV) in a range of about 0.05hr⁻¹ to about 0.45 hr⁻¹, more preferably in a range of about 0.15 hr⁻¹to about 0.35 hr⁻¹. The difference between hydrocracking andhydrotreating can also be expressed in terms of resid conversion(wherein hydrocracking results in the substantial conversion of higherboiling to lower boiling hydrocarbons, while hydrotreating does not).The hydroprocessing systems disclosed herein can result in a residconversion in a range of about 40% to about 90%, preferably in a rangeof about 55% to about 80%. The preferred conversion range typicallydepends on the type of feedstock because of differences in processingdifficulty between different feedstocks. Typically, conversion will beat least about 5% higher, preferably at least about 10% higher, comparedto operating an ebullated bed reactor prior to upgrading to utilize adual catalyst system as disclosed herein.

Material 426 in ebullated bed reactor 430 is continuously recirculatedfrom upper heterogeneous catalyst free zone 450 to lower heterogeneouscatalyst free zone 448 by means of a recycling channel 452 connected toan ebullating pump 454. At the top of recycling channel 452 is afunnel-shaped recycle cup 456 through which material 426 is drawn fromupper heterogeneous catalyst free zone 450. Recycled material 426 isblended with fresh conditioned feedstock 411 and hydrogen gas 420.

Fresh heterogeneous catalyst 444 is introduced into ebullated bedreactor 430 through a catalyst inlet tube 458, and spent heterogeneouscatalyst 444 is withdrawn through a catalyst withdrawal tube 460.Whereas the catalyst withdrawal tube 460 is unable to differentiatebetween fully spent catalyst, partially spent but active catalyst, andfresh catalyst, the existence of dispersed metal sulfide catalystparticles 424 provides additional catalytic activity, within expandedcatalyst zone 442, recycle channel 452, and lower and upperheterogeneous catalyst free zones 448, 450. The addition of hydrogen tohydrocarbons outside of heterogeneous catalyst 444 minimizes formationof sediment and coke precursors, which are often responsible fordeactivating the heterogeneous catalyst.

Ebullated bed reactor 430 further includes an outlet port 438 at or nearthe top through which converted material 440 is withdrawn. Convertedmaterial 440 is introduced into hot separator or distillation tower 404.Hot separator or distillation tower 404 separates one or more volatilefractions 405, which is/are withdrawn from the top of hot separator 404,from a resid fraction 407, which is withdrawn from a bottom of hotseparator or distillation tower 404. Resid fraction 407 containsresidual metal sulfide catalyst particles, schematically depicted ascatalyst particles 424. If desired, at least a portion of resid fraction407 can be recycled back to ebullated bed reactor 430 in order to formpart of the feed material and to supply additional metal sulfidecatalyst particles. Alternatively, resid fraction 407 can be furtherprocessed using downstream processing equipment, such as anotherebullated bed reactor. In that case, separator 404 can be an interstageseparator.

In some embodiments, operating the upgraded ebullated bed reactor atsimilar or higher severity and/or throughput while producing vacuumresidue products of improved quality can result in a rate of equipmentfouling that is similar to or less than when initially operating theebullated bed reactor. In general, improving the quality of vacuumresidue products can reduce equipment fouling by reducing one or more ofviscosity, asphaltene content, carbon content, sediment content,nitrogen content, and sulfur content.

V. Vacuum Residues of Improved Quality

As disclosed herein, upgrading an ebullated bed hydroprocessing systemto utilize a dual catalyst system can substantially improve the qualityof vacuum residues that remain after upgrading heavy oil and removinglighter and more valuable fractions. Vacuum residue products of improvedquality are characterized by one or more of reduced viscosity, reducedspecific gravity (increased API gravity), reduced asphaltene content,reduced carbon content, reduced sulfur content, and reduced sedimentcontent.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in viscosity (e.g., as measured byBrookfield Viscosity at 300° F.) of at least 10%, 15%, 20%, 25%, 30%,40%, 50%, 60%, or 70% compared to when initially operating the ebullatedbed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in asphaltene content of at least 5%,7.5%, 10%, 12.5%, 15%, 20%, 25%, or 30% compared to when initiallyoperating the ebullated bed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in micro carbon residue content (e.g.,as measured by MCR content) of at least 2%, 4%, 6%, 8%, 10%, 12.5%, 15%,or 20% compared to when initially operating the ebullated bed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in sulfur content of at least 5%, 7.5%,10%, 15%, 20%, 25%, 30%, or 35% compared to when initially operating theebullated bed reactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in density, which can be expressed as anincrease in ° API Gravity of at least 0.4, 0.6, 0.8, 1.0, 1.3, 1.6, 2.0,2.5 or 3.0, compared to when initially operating the ebullated bedreactor.

In some embodiments, the vacuum residue product of improved quality canbe characterized by a reduction in sediment content of at least 2%, 4%,6%, 8%, 10%, 12.5%, 15%, or 20% compared to when initially operating theebullated bed reactor.

In general, vacuum residue products can be used for (1) fuel oil, (2)solvent deasphalting, (3) coking, (4) power plant fuel, and/or (5)partial oxidation (e.g., gasification to generate hydrogen). Because ofrestrictions on the amount of contaminants that are permitted in thevacuum residue products, improving their quality using the dual catalystsystem hydroprocessing systems disclosed herein can reduce the amount ofmore expensive cutter stocks otherwise required to bring the vacuumresidue within specification. It can also reduce the burden on theoverall process where the cutter stock is otherwise needed elsewhere forefficient operation of the overall hydroprocessing system.

Results from ebullated bed units have shown that bottoms products (i.e.,vacuum tower bottoms, VTB, fuel oil) can be produced with improvedquality through the use of a dual catalyst system while stillmaintaining at least the same, or even higher, production rate ofconverted products compared to the non-dual catalyst operation.

In addition, when an ebullated bed is upgraded to use a dual catalystsystem and the production rate of converted products is raisedsubstantially above initial conditions, the bottoms product can bemaintained at least at equal quality, when it would otherwise beexpected to have reduced quality without the use of the dual catalystsystem.

In a given ebullated bed system, the rate of production of convertedproducts can be limited by minimum requirements for the quality of thevacuum tower bottoms product. Other things being equal, as productionrate is increased (typically by some combination of increased reactortemperature, throughput, and resid conversion) the quality of bottomsproducts is reduced, and will at some point fall below a requirement orspecification which governs the sale or use of the bottoms product. Whenthis occurs, the economics of the overall refinery operation isnegatively impacted due to loss of value from sales of the bottomsproduct. As a result, a refinery will adjust the operation of theirebullated bed system in order to ensure that bottoms product ofacceptable quality is produced. Use of the dual catalyst system canpermit an operator to maintain their economic viability.

With the dual catalyst system, the bottoms product quality is improvedcompared to what would be expected under comparable conditions withoutthe dual catalyst system. This affords ebullated bed operators addedflexibility in unit operation. For example, the ebullated bed unit maybe operated in a fashion that results in a net improvement in bottomsquality. This can provide an economic advantage in that it can allow thebottoms product to be sold for a higher price by meeting thespecifications for a more value-added use of the material. Alternately,the ebullated bed unit may be pushed to higher levels of production rateof converted products, while still maintaining at least equal bottomsquality. This provides an economic advantage by increasing the sales ofhigh-value converted products (naphtha, diesel, vacuum gas oil) withoutnegatively impacting the marketability of the bottoms product.

Higher rates of production of converted products can be achieved byincreasing “reactor severity”, which is the combination of reactortemperature, throughput, and resid conversion that defines the overallreactor performance. Increased reactor severity, and therefore increasedproduction rate, can be achieved by different combinations of conditionchanges, such as (a) increased temperature/conversion at constantthroughput, (b) increased throughput/temperature at constant conversion,and (c) increased throughput, temperature, and conversion.

Viscosity of vacuum tower bottoms products is often measured in units ofcP (centipoise). The magnitude of the change in viscosity with dualcatalyst usage depends on multiple factors, including the type of heavyoil feedstock and the ebullated bed operating conditions. Underconditions of equal production rate of converted products, the dualcatalyst has been shown to reduce the viscosity of vacuum tower bottomsby:

-   -   40-50% for Ural vacuum resid feedstock;    -   30-50% for Arab Medium vacuum resid feedstock;    -   60-70% for Athabasca vacuum resid feedstock;    -   40-50% for Maya atmospheric resid feedstock.

The API Gravity of VTB products is measured in degrees)(° API gravity,which is related to the specific gravity of the material through theformula: SG (at 60 F)=141.5/(API Gravity+131.5). VTB products have highdensity and low API gravity, with the gravity near zero, or even belowzero. Under conditions of equal production rate of converted products,the dual catalyst system has been shown to increase the API gravity ofvacuum tower bottoms by:

-   -   ˜1° API for Arab Medium vacuum resid feedstock;    -   up to 10° API for Athabasca vacuum resid feedstock;    -   ˜0.2° API for Maya atmospheric resid feedstock.

Asphaltene content can be measured in weight percent content and definedas the difference between heptane insoluble content and tolueneinsolubles content. Asphaltenes defined in this fashion are commonlyreferred to as “C₇ asphaltenes”. An alternate definition is pentaneinsolubles minus toluene insolubles, commonly referred to as “C₅asphaltenes”. In the following examples, the C₇ asphaltene definition isused.

Under conditions of equal production rate of converted products, thedual catalyst system has been shown to reduce the asphaltene content ofVTB product by:

-   -   15-20% (relative) for Ural vacuum resid feedstock    -   at least 30-40% (relative) for Arab Medium vacuum resid        feedstock    -   ˜50% (relative) for Athabasca vacuum resid feedstock.

Carbon residue content is measured in weight percent content by themicrocarbon residue (MCR) or Conradson carbon residue (CCR) method.Under conditions of equal production rate of converted products, thedual catalyst system has been shown to reduce the MCR content of VTBproduct by:

-   -   10-15% (relative) for Ural vacuum resid feedstock;    -   ˜30% (relative) for Athabasca vacuum resid feedstock.

Sulfur content is measured in weight percent content. Under conditionsof equal production rate of converted products, the dual catalyst systemhas been shown to reduce the sulfur content of VTB product by:

-   -   ˜30% (relative) for Ural vacuum resid feedstock;    -   25-30% (relative) for Arab Medium vacuum resid feedstock;    -   Up to 40% (relative) for Athabasca vacuum resid feedstock.

VI. Experimental Studies and Results

The following test studies demonstrate the effects and advantages ofupgrading an ebullated bed reactor to use a dual catalyst systemcomprised of a heterogeneous catalyst and dispersed metal sulfidecatalyst particles when hydroprocessing heavy oil. In particular, thetest studies demonstrate the improvements in vacuum residue productquality that can be achieved by use of the present invention. The pilotplant used for this test was designed according to FIG. 5. Asschematically illustrated in FIG. 5, a pilot plant 500 with twoebullated bed reactors 512, 512′ connected in series was used todetermine the difference between using a heterogeneous catalyst byitself when processing heavy oil feedstocks and a dual catalyst systemcomprised of a heterogeneous catalyst in combination with dispersedmetal sulfide catalyst particles (i.e., dispersed molybdenum disulfidecatalyst particles).

For the following test studies, a heavy vacuum gas oil was used as thehydrocarbon diluent. The precursor mixture was prepared by mixing anamount of catalyst precursor with an amount of hydrocarbon diluent toform a catalyst precursor mixture and then mixing an amount of thecatalyst precursor mixture with an amount of heavy oil feedstock toachieve the target loading of dispersed catalyst in the conditionedfeedstock. As a specific illustration, for one test study with a targetloading of 30 ppm dispersed metal sulfide catalyst in the conditionedfeedstock (where the loading is expressed based on metal concentration),the catalyst precursor mixture was prepared with a 3000 ppmconcentration of metal.

The feedstocks and operating conditions for the actual tests are moreparticularly identified below. The heterogeneous catalyst was acommercially available catalyst commonly used in ebullated reactors.Note that for comparative test studies for which no dispersed metalsulfide catalyst was used, the hydrocarbon diluent (heavy vacuum gasoil) was added to the heavy oil feedstock in the same proportion as whenusing a diluted precursor mixture. This ensured that the backgroundcomposition was the same between tests using the dual catalyst systemand those using only the heterogeneous (ebullated bed) catalyst, therebyallowing test results to be compared directly.

Pilot plant 500 more particularly included a high shear mixing vessel502 for blending a precursor mixture comprised of a hydrocarbon diluentand catalyst precursor (e.g., molybdenum 2-ethylhexanoate) with a heavyoil feedstock (collectively depicted as 501) to form a conditionedfeedstock. Proper blending can be achieved by first pre-blending thecatalyst precursor with a hydrocarbon diluent to form a precursormixture.

The conditioned feedstock is recirculated out and back into the mixingvessel 502 by a pump 504, similar to a surge vessel and pump-around. Ahigh precision positive displacement pump 506 draws the conditionedfeedstock from the recirculation loop and pressurizes it to the reactorpressure. Hydrogen gas 508 is fed into the pressurized feedstock and theresulting mixture is passed through a pre-heater 510 prior to beingintroduced into first ebullated bed reactor 512. The pre-heater 510 cancause at least a portion of the catalyst precursor within theconditioned feedstock to decompose and form active catalyst particles insitu within the feedstock.

Each ebullated bed reactor 512, 512′ can have a nominal interior volumeof about 3000 ml and include a mesh wire guard 514 to keep theheterogeneous catalyst within the reactor. Each reactor is also equippedwith a recycle line and recycle pump 513, which provides the requiredflow velocity in the reactor to expand the heterogeneous catalyst bed.The combined volume of both reactors and their respective recycle lines,all of which are maintained at the specified reactor temperature, can beconsidered to be the thermal reaction volume of the system and can beused as the basis for calculation of the Liquid Hourly Space Velocity(LHSV). For these examples, “LHSV” is defined as the volume of vacuumresidue feedstock fed to the reactor per hour divided by the thermalreaction volume.

A settled height of catalyst in each reactor is schematically indicatedby a lower dotted line 516, and the expanded catalyst bed during use isschematically indicated by an upper dotted line 518. A recirculatingpump 513 is used to recirculate the material being processed from thetop to the bottom of reactor 512 to maintain steady upward flow ofmaterial and expansion of the catalyst bed.

Upgraded material from first reactor 512 is transferred together withsupplemental hydrogen 520 into second reactor 512′ for furtherhydroprocessing. A second recirculating pump 513′ is used to recirculatethe material being processed from the top to the bottom of secondreactor 512′ to maintain steady upward flow of material and expansion ofthe catalyst bed.

The further upgraded material from second reactor 512′ is introducedinto a hot separator 522 to separate low-boiling hydrocarbon productvapors and gases 524 from a liquid fraction 526 comprised of unconvertedheavy oil. The hydrocarbon product vapors and gases 524 are cooled andpass into a cold separator 528, where they are separated into gases 530and converted hydrocarbon products, which are recovered as separatoroverheads 532. The liquid fraction 526 from hot separator 522 isrecovered as separator bottoms 534, which can be used for analysis.

Examples 1-6

Examples 1-6 were conducted in the abovementioned pilot plant and testedthe ability of an upgraded ebullated bed reactor that employed a dualcatalyst system to produce vacuum residue product with improved qualitycompared to an ebullated bed system operated with only the heterogeneouscatalyst. For this set of examples, the heavy oil feedstock was a Uralvacuum residue (Ural VR) with a nominal cut point of 1000° F. (538° C.).As described above, a conditioned feedstock was prepared by mixing anamount of catalyst precursor mixture with an amount of heavy oilfeedstock to a final conditioned feedstock that contained the requiredamount of dispersed catalyst. The exception to this were tests for whichno dispersed catalyst was used, in which case heavy vacuum gas oil wassubstituted for the catalyst precursor mixture at the same proportion.

The conditioned feedstock was fed into the pilot plant system of FIG. 5,which was operated using specific parameters. The parameters used foreach of Examples 1 to 6 and the corresponding vacuum residue productquality results are set forth in Table 3.

TABLE 3 Example Run Parameters 1 2 3 4 5 6 Dispersed Catalyst  0  0  30 30  50  50 Concentration (ppm Mo) Reactor Temperature (° F./° C.) 789801 789 801 789 801 (421) (427) (421) (427) (421) (427) LHSV, vol.feed/vol. reactor/hr    0.24    0.24    0.24    0.24 0.24    0.24 ResidConversion, based on 60% 68% 58% 67% 56% 66% 1000° F.+, % Properties of1000° F.+ Vacuum Residue Product Cut Brookfield viscosity, cp at 300° F.123 146  66  93  27  34 Sulfur Content, wt %    1.47    1.69    1.28   1.48    1.05    1.12 C₇ Asphaltene Content, wt %   12.9   15.8   10.5  13.2   10.0   12.3 Carbon Residue Content, wt %   27.3   31.8   23.5  28.0   23.2   26.3 (by MCR)

Examples 1 and 2 utilized a heterogeneous catalyst to simulate anebullated bed reactor prior to being upgraded to employ a dual catalystsystem according to the invention. Examples 3-6 utilized a dual catalystsystem comprised of the same heterogeneous catalyst of Examples 1 and 2and also dispersed molybdenum sulfide catalyst particles. Theconcentration of dispersed molybdenum sulfide catalyst particles in thefeedstock was measured as concentration in parts per million (ppm) byweight of molybdenum metal (Mo) provided by the dispersed catalyst. Thefeedstock of Examples 1 and 2 included no dispersed catalyst (0 ppm Mo),the feedstock of Examples 3 and 4 included dispersed catalyst at aconcentration of 30 ppm Mo, and the feedstock of Examples 5 and 6included dispersed catalyst at a higher concentration of 50 ppm Mo.

For each of Examples 1-6, the pilot unit operation was maintained for aperiod of 5 days. Steady state operating data and product samples werecollected during the final 3 days of each example test. To determine thequality of the vacuum residue product, samples of separator bottomsproduct were collected during the steady-state portion of the test andsubjected to laboratory distillation using the ASTM D-1160 method toobtain a sample of vacuum residue product. For Examples 1-6, the vacuumresidue product was based on a nominal cut point of 1000° F. (538° C.).

Example 1 was the baseline test in which Ural VR was hydroprocessed at atemperature of 789° F. (421° C.) and a space velocity of 0.24 hr⁻¹,resulting in a resid conversion (based on 1000° F.+, %) of 60%. InExample 2, the temperature was 801° F. (427° C.), resulting in a residconversion of 68%. Examples 3 and 4 were operated at the same parametersas Examples 1 and 2, respectively, except that the dual catalyst systemof the present invention was now used, with a dispersed catalystconcentration of 30 ppm Mo. Likewise, Examples 5 and 6 employed the samecombination of parameters, but at a higher dispersed catalystconcentration of 50 ppm Mo.

The dual catalyst system of Examples 3-6 resulted in significantimprovements in vacuum residue product quality relative to the baselinetests of Examples 1 and 2. This is illustrated graphically in FIG. 6,which shows a chart of Brookfield viscosity (measured at 300° F.) of thevacuum residue product for Examples 1-6. To aid in making comparisons,results are plotted as a function of resid conversion, allowing theresults to be compared at equal conversion. Across the entire range ofresid conversion tested in Examples 1-6, there is a significantimprovement (reduction) in product viscosity when the dual catalystsystem is used.

FIG. 7 shows the results for sulfur content of the vacuum residueproduct. Again, sulfur content is reduced significantly by the use ofthe dual catalyst system.

Asphaltene content of the vacuum residue product is also reduced by useof the dual catalyst system, as shown in FIG. 8. Asphaltene content isdefined based on C₇ asphaltenes, which are calculated as the differencebetween the heptane insoluble content and the toluene insoluble content.Here, the response differs somewhat from the viscosity and sulfurcontent, in that most of the improvement is achieved through use of 30ppm dispersed catalyst.

Similar behavior is observed for the carbon residue content, measured bythe microcarbon residue (MCR) method. These results are shown in FIG. 9,and show a significant reduction with the use of 30 ppm dispersedcatalyst.

Examples 7-13

Examples 7-13 were conducted with the same equipment and methods ofExamples 1-6, except that the heavy oil feedstock was a refinery feedmix based primarily on Arab Medium vacuum residue (Arab Medium VR), alsowith a nominal cut point of 1000° F. (538° C.). Methods for thepreparation of conditioned heavy oil feedstock were the same asdescribed for Examples 1-6.

The conditioned feedstock was fed into the pilot plant system of FIG. 5,which was operated using specific parameters. The parameters used foreach of Examples 7-13 and the corresponding vacuum residue productquality results are set forth in Table 4.

TABLE 4 Example Run Parameters 7 8 9 10 11 12 13 Dispersed Catalyst  0 0  30  30  50  50  50 Concentration (ppm Mo) Reactor Temperature (°F./° C.) 815 803 815 803 815 814 802 (435) (428) (435) (428) (435) (434)(428) LHSV, vol. feed/vol. reactor/hr    0.24    0.24    0.24    0.24   0.24    0.24    0.24 Resid Conversion, based on 81% 73% 80% 71% 79%81% 72% 1000° F.+, % Properties of 1000° F.+ Vacuum Residue Product CutAPI Gravity (°)   −4.1   −0.2   −1.4   0.7   −1.6   −2.7    0.6Brookfield viscosity, cp at 572 297 199 177 203 201 127 300° F. SulfurContent, wt %    3.13    3.25    2.52    2.87    2.46    2.35    2.47

Examples 7 and 8 utilized a heterogeneous catalyst to simulate anebullated bed reactor prior to being upgraded to employ a dual catalystsystem according to the invention. Examples 9-13 utilized a dualcatalyst system comprised of the same heterogeneous catalyst of Examples7 and 8 and also dispersed molybdenum sulfide catalyst particles. Theconcentration of dispersed molybdenum sulfide catalyst particles in thefeedstock was measured as concentration in parts per million (ppm) byweight of molybdenum metal (Mo) provided by the dispersed catalyst. Thefeedstock of Examples 7 and 8 included no dispersed catalyst (0 ppm Mo),the feedstock of Examples 9 and 10 included dispersed catalyst at aconcentration of 30 ppm Mo, and the feedstock of Examples 11-13 includeddispersed catalyst at a higher concentration of 50 ppm Mo.

Similar to Examples 1-6, the pilot unit operations of Examples 7-13 weremaintained for a period of 5 days, with steady state operating data andproduct samples being collected during the final 3 days of each exampletest. To determine the quality of the vacuum residue product, samples ofseparator bottoms product were collected during the steady-state portionof the test and subjected to laboratory distillation using the ASTMD-1160 method to obtain a sample of vacuum residue product. For Examples7-13, the vacuum residue product was based on a nominal cut point of1000° F. (538° C.).

Examples 7 and 8 were baseline tests in which the feedstock based onArab Medium VR was hydroprocessed at a temperatures of 815° F. (435° C.)and of 803° F. (428° C.), respectively, and a space velocity of about0.25 hr⁻¹, resulting in resid conversion (based on 1000° F.+, %) of 81%and 73%, respectively. Examples 9 and 10 were operated at the sametemperature and space velocity and similar resid conversions as Examples7 and 8, respectively, except that the dual catalyst system of thepresent invention was used, with a dispersed catalyst concentration of30 ppm Mo. Examples 11 and 12 used the same parameters as Example 7, andExample 13 was analogous to Example 8, but at a higher dispersedcatalyst concentration of 50 ppm Mo.

The dual catalyst system of Examples 9-13 resulted in significantimprovements in vacuum residue product quality relative to the baselinetests of Examples 7 and 8 for Arab Medium-based feedstock. This isillustrated graphically in FIG. 10, which shows the ° API gravity of the1000° F.+ vacuum residue product cut. While there is relatively littledifference between the API gravity results at the low end of the residconversion range, there is a significant increase in API gravity (i.e.,reduction in density, or specific gravity) for the vacuum residueproduct at high resid conversion when the dual catalyst system is used(Examples 9, 11, and 12).

FIG. 11 shows the results for sulfur content of the vacuum residue cutfor Examples 7-13. Sulfur content was reduced through the use of thedual catalyst system, with the reduction being achieved across theentire range of resid conversion tested.

FIG. 12 shows the results for the Brookfield viscosity (measured at 300°F.) of the vacuum residue product cut. There was a significant reductionin viscosity through the use of the dual catalyst system, with theimprovement being especially notable at higher resid conversion. In thiscase, significant improvement was achieved at 30 ppm dispersed catalyst.

Examples 14-19

Examples 14-19 were conducted with the same equipment and methods ofExamples 1-6, except that the heavy oil feedstock was an Athabascavacuum residue (Athabasca VR), with a nominal cut point of 975° F. (524°C.). Methods for the preparation of conditioned heavy oil feedstock werethe same as described for Examples 1-6.

The conditioned feedstock was fed into the pilot plant system of FIG. 5,which was operated using specific parameters. The parameters used foreach of Examples 14-19 and the corresponding vacuum residue productquality results are set forth in Table 5.

TABLE 5 Example Run Parameters 14 15 16 17 18 19 Dispersed Catalyst  0 0  0  50  50  50 Concentration (ppm Mo) Reactor Temperature (° F./° C.)798 814 824 799 814 824 (426) (434) (440) (426) (434) (440) LHSV, vol.feed/vol. reactor/hr    0.28    0.28    0.28    0.28    0.28    0.28Resid Conversion, based on 72% 80% 87% 74% 81% 86% 1000° F.+, %Properties of 1000° F.+ Vacuum Residue Product Cut API Gravity (°)   6.5   −2.8   −7.2    6.6    3.4    0.1 Sulfur Content, wt %    1.68   2.07    2.51    1.60    1.62    1.81 Brookfield viscosity, cp at 300°F. n/a n/a 3020  250 693 910 Heptane insolubles content, wt % n/a n/a  29.5    8.1   12.0   16.2 Carbon Residue Content, wt % n/a n/a   42.7  22.1   24.2   32.2 (by MCR)

Examples 14-16 utilized a heterogeneous catalyst to simulate anebullated bed reactor prior to being upgraded to employ a dual catalystsystem according to the invention. Examples 17-19 utilized a dualcatalyst system comprised of the same heterogeneous catalyst of Examples14-16 and dispersed molybdenum sulfide catalyst particles. Theconcentration of dispersed molybdenum sulfide catalyst particles in thefeedstock was measured as concentration in parts per million (ppm) byweight of molybdenum metal (Mo) provided by the dispersed catalyst. Thefeedstock of Examples 14-16 included no dispersed catalyst (0 ppm Mo)and the feedstock of Examples 17-19 included dispersed catalyst at ahigher concentration of 50 ppm Mo.

Examples 14 and 17 were operated for a period of 6 days, withsteady-state data and samples being collected during the final 3 days ofthe test. The remaining tests were operated for shorter durations.Examples 15 and 18 were operated for about 3 days, with operating dataand samples collected during the final 2 days. Examples 17 and 19 wereonly operated for about 2 days, with data and samples only collectedduring the last day.

As with previous examples, the quality of the vacuum residue productsfrom each test was determined by collecting samples of separator bottomsproduct during the steady-state portion of the test and subjecting themto laboratory distillation using the ASTM D-1160 method to obtain asample of vacuum residue product. For Examples 14-19, the vacuum residueproduct was based on a nominal cut point of 975° F. (524° C.).

Examples 14-16 were baseline tests in which the Athabasca VR feedstockwas hydroprocessed at temperatures of 798° F. (425.5° C.) 814° F. (434°C.), and 824° F. (440° C.), respectively, and a space velocity of 0.28hr⁻¹, resulting in resid conversions (based on 975° F.+, %) of 72%, 80%and 87%, respectively. Examples 17-19 were operated at the sametemperature and space velocity and similar resid conversion as Examples14-16, respectively, except that the dual catalyst system of the presentinvention was used, with a dispersed catalyst concentration of 50 ppmMo.

The dual catalyst system of Examples 17-19 resulted in significantimprovements in vacuum residue product quality relative to the baselinetests of Examples 14-16 for the Athabasca VR feedstock.

FIG. 13 shows the results for API gravity of the 975° F.+ vacuum residueproduct cut. Product gravity is increased (i.e. product density, orspecific gravity, decreased) significantly through the use of the dualcatalyst system, with a greater degree of improvement at higher residconversion.

Similarly, FIG. 14 shows the results for sulfur content of the vacuumresidue product. Again, there is a significant improvement (i.e.,reduction in sulfur content) by the use of the dual catalyst system,with the magnitude of the improvement increasing with increasing residconversion.

FIG. 15 shows results for the Brookfield viscosity of the vacuum residuecut, measured at 266° F. (130° C.). Viscosity data are not available forExamples 14 and 15, so only Examples 16-19 are represented in thisfigure. The data show a major improvement in product viscosity throughthe use of the dual catalyst system.

FIG. 16 shows results for the heptane insoluble (HI) content of thevacuum residue cut. Heptane insoluble content is similar to the C₇asphaltene content. As with the viscosity data, HI results are notavailable for Examples 14 and 15. The results of Examples 16-19 show asignificant reduction in HI content through the use of the dual catalystsystem.

FIG. 17 shows the results for carbon residue content of the vacuumresidue product cut, measured by the microcarbon residue (MCR) method.Again, data for Examples 14 and 15 are not available, but the results ofExamples 16-19 show a significant reduction in MCR content with the useof the dual catalyst system.

Examples 20-21

Examples 20 and 21 provide a further comparison and illustration of thebenefits associated with improving the quality of vacuum residue withrespect to sulfur content and the amount of cutter stock required tobring a typical vacuum residue into conformance with fuel oilspecifications. Example 20 is based on actual results when operating aconventional ebullated bed hydroprocessing system using a heterogeneouscatalyst to produce a vacuum tower bottoms (VTB) product from a Uralsvacuum resid (VR) feedstock. Example 21 is based on actual results whenoperating an upgraded ebullated bed hydroprocessing system using a dualcatalyst system including a heterogeneous catalyst and dispersed metalsulfide catalyst particles to produce a vacuum tower bottoms (VTB)product of improved quality from the Urals VR feedstock. The comparativeresults are shown in Table 6.

TABLE 6 Example Conditions and Results 20 21 Feedstock Type Urals UralsResid Conversion, % 58 66 VTB, t/h 105 85 VTB Sulfur, wt % 1.65 1.10Cutter stock Sulfur, wt % 0.1 0.1 Cutter stock required for 75 9 1%sulfur fuel oil, t/h

From Examples 20 and 21 it can be seen that using the dual catalystsystem of the invention can reduce the amount of cutter stock requiredto bring the VTB in line with prescriptive fuel oil sulfur standards. Inthis case, the reduction in cutter stock was 88%. Because cutter stocksare by definition higher quality fractions, they have a retail valuegreater than VTB. Reducing the amount of cutter stock required to bringfuel oil within specification can represent a substantial cost savings.It also reduces the burden on the overall process where the cutter stockis otherwise required for efficient operation of the overallhydroprocessing system.

Examples 20 and 21 highlight the significance/benefit of increased residconversion between the two examples. Because Example 21 has both ahigher resid conversion and a higher quality bottoms product, there is adouble benefit for the amount of cutter stock needed. Part of thereduction in cutter stock comes from an overall reduction in the amountVTB product (due to higher resid conversion), and part comes from thehigher quality of VTB that is produced. In both cases, the amount ofcutter stock otherwise required to dilute the VTB product is reduced.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method of upgrading an ebullated bed hydroprocessing system thatincludes one or more ebullated bed reactors to improve vacuum residuequality, comprising: operating an ebullated bed reactor using aheterogeneous catalyst to hydroprocess heavy oil at an initial rate ofproduction of converted products and produce an initial rate and qualityof bottoms product; thereafter upgrading the ebullated bed reactor tooperate using a dual catalyst system comprised of dispersed metalsulfide catalyst particles and heterogeneous catalyst; and operating theupgraded ebullated bed reactor using the dual catalyst system tohydroprocess heavy oil at a rate of production of converted products atleast as high as the initial rate and producing bottoms product with ahigher quality than the initial quality.
 2. The method of claim 1,wherein the heavy oil comprises at least one of heavy crude oil, oilsands bitumen, residuum from refinery processes, atmospheric towerbottoms having a nominal boiling point of at least 343° C. (650° F.),vacuum tower bottoms having a nominal boiling point of at least 524° C.(975° F.), resid from a hot separator, resid pitch, products fromsolvent deasphalting, or vacuum residue.
 3. The method of claim 1, wherethe bottoms product is a vacuum tower bottoms product (vacuum residueproduct).
 4. The method of claim 1, where the bottoms product is anatmospheric tower bottoms product (atmospheric residue product).
 5. Themethod of claim 1, wherein the bottoms product produced by the upgradedebullated bed reactor has a viscosity that is reduced relative to aninitial viscosity of the bottoms product of initial quality.
 6. Themethod of claim 5, wherein the viscosity of the bottoms product producedby the upgraded ebullated bed reactor is at least 10% lower, or least25% lower, or at least 40% lower, than the initial viscosity.
 7. Themethod of claim 1, wherein the bottoms product produced by the upgradedebullated bed reactor has an API gravity that is increased relative toan initial API gravity of the bottoms product of initial quality.
 8. Themethod of claim 7, wherein the API gravity of the bottoms productproduced by the upgraded ebullated bed reactor is at least 0.1 degreeAPI higher, or at least 0.5 degree API higher, or at least 1 API degreehigher, than the initial API gravity.
 9. The method of claim 1, whereinthe bottoms product produced by the upgraded ebullated bed reactor hasan asphaltene content that is reduced relative to an initial asphaltenecontent of the bottoms product of initial quality.
 10. The method ofclaim 9, wherein the asphaltene content of the bottoms product producedby the upgraded ebullated bed reactor is at least 10% lower, or at least20% lower, or at least 30% lower, than the initial asphaltene content.11. The method of claim 1, wherein the bottoms product produced by theupgraded ebullated bed reactor has a carbon residue content that isreduced relative to an initial carbon residue content of the bottomsproduct of initial quality.
 12. The method of claim 11, wherein thecarbon residue content of the bottoms product produced by the upgradedebullated bed reactor is at least 5% lower, or at least 10% lower, or atleast 20% lower, than the initial carbon residue content.
 13. The methodof claim 1, wherein the bottoms product produced by the upgradedebullated bed reactor has a sulfur content that is reduced relative toan initial sulfur content of the bottoms product of initial quality. 14.The method of claim 13, wherein the sulfur content of the bottomsproduct produced by the upgraded ebullated bed reactor is at least 10%lower, or at least 20% lower, or at least 30% lower, than the initialsulfur content.
 15. The method of claim 1, wherein the bottoms productproduced by the upgraded ebullated bed reactor has a sediment contentthat is reduced relative to an initial sediment content of the bottomsproduct of initial quality.
 16. The method of claim 15, wherein thesediment content of the bottoms product produced by the upgradedebullated bed reactor is at least 5% lower, or at least 10% lower, or atleast 20% lower, than the initial sediment content.
 17. The method ofclaim 1, wherein the dispersed metal sulfide catalyst particles are lessthan 1 μm in size, or less than about 500 nm in size, or less than about100 nm in size, or less than about 25 nm in size, or less than about 10nm in size.
 18. The method of claim 17, the dispersed metal sulfidecatalyst particles being formed in situ within the heavy oil from acatalyst precursor.
 19. The method of claim 18, further comprisingmixing the catalyst precursor with a diluent hydrocarbon to form adiluted precursor mixture, blending the diluted precursor mixture withthe heavy oil to form conditioned heavy oil, and heating the conditionedheavy oil to decompose the catalyst precursor and form the dispersedmetal sulfide catalyst particles in situ.
 20. The method of claim 1,wherein operating the upgraded ebullated bed includes operating at asame or higher severity than when initially operating the ebullated bed.21. The method of claim 1, wherein operating the upgraded ebullated bedincludes operating at a same or higher throughput than when initiallyoperating the ebullated bed.
 22. The method of claim 1, whereinoperating the upgraded ebullated bed includes operating at a same orhigher temperature than when initially operating the ebullated bed. 23.The method of claim 1, wherein operating the upgraded ebullated bedincludes operating at a same or higher conversion than when initiallyoperating the ebullated bed.
 24. A method of upgrading an ebullated bedhydroprocessing system that includes one or more ebullated bed reactorsto improve vacuum residue quality, comprising: operating an ebullatedbed reactor using a heterogeneous catalyst to hydroprocess heavy oil atan initial rate of production of converted products and produce aninitial rate and quality of bottoms product; thereafter upgrading theebullated bed reactor to operate using a dual catalyst system comprisedof dispersed metal sulfide catalyst particles and heterogeneouscatalyst; and operating the upgraded ebullated bed reactor using thedual catalyst system to hydroprocess heavy oil at a rate of productionof converted products that is higher than the initial rate and producingbottoms product of same or higher quality than the initial quality. 25.The method of claim 24, where the bottoms product is a vacuum towerproduct (vacuum residue product).
 26. The method of claim 24, where thebottoms product is an atmospheric tower bottoms product (atmosphericresidue product).
 27. The method of claim 24, wherein operating theupgraded ebullated bed at a higher rate of production of convertedproducts includes operating at higher temperature and/or conversionwhile maintaining similar throughput.
 28. The method of claim 24,wherein operating the upgraded ebullated bed at a higher rate ofproduction of converted products includes operating at higher throughputand/or temperature while maintaining similar conversion.
 29. The methodof claim 24, wherein operating the upgraded ebullated bed at a higherrate of production of converted products includes operating at highertemperature, throughput and conversion.
 30. The method of claim 24,wherein the bottoms product produced by the upgraded ebullated bed has aviscosity that is no higher than a viscosity of the bottoms product ofinitial quality.
 31. The method of claim 24, wherein the bottoms productproduced by the upgraded ebullated bed has an asphaltene content that isno higher than an asphaltene content of the bottoms product of initialquality.
 32. The method of claim 24, wherein the bottoms productproduced by the upgraded ebullated bed has a carbon residue content thatis no higher than a carbon residue content of the bottoms product ofinitial quality.
 33. The method of claim 24, wherein the bottoms productproduced by the upgraded ebullated bed has a sulfur content that is nohigher than a sulfur content of the bottoms product of initial quality.34. The method of claim 24, wherein the bottoms product produced by theupgraded ebullated bed has an API gravity at least as high as an APIgravity of the bottoms product of initial quality.
 35. The method ofclaim 24, wherein the bottoms product produced by the upgraded ebullatedbed has a sediment content no higher than a sediment content of thebottoms product of initial quality.